In שמואל א יט it says in reference to David's escape from Saul:
וַתִּקַּ֨ח מִיכַ֜ל אֶת־הַתְּרָפִ֗ים וַתָּ֙שֶׂם֙ אֶל־הַמִּטָּ֔ה וְאֵת֙ כְּבִ֣יר הָֽעִזִּ֔ים שָׂ֖מָה מְרַֽאֲשֹׁתָ֑יו וַתְּכַ֖ס בַּבָּֽגֶד׃
Michal then took the household idol, laid it on the bed, and covered it with a cloth; and at its head she put a net of goat’s hair. (Sefaria, using the JPS translation)
Why did David have a household idol?
The question is what does the word Terafim / תרפים mean and connote.
The Targum translates it as צלמניא or forms.
Rashi there writes:
את התרפים. עשויים בדמות גוף אדם
A manlike figure. Made in the likeness of a human body.
So he is explaining why she put it there. The Terafim were a decoy to mislead Shaul's men. Rashi doesn't indicate this human figure's purpose.
Radak writes similarly, and addreses their purpose:
וענין התרפים יש מפרשים כי הם עבודת גילולים כמו התרפים אשר ללבן שגנבתם רחל ולבן עובד עבודת גילולים היה כמו שאמר לה למה גנבת את אלהי וחלילה חלילה שהיה בבית דוד עבודת גילולים ויש אומרים שהוא כלי הנחשת העשוי לדעת חלקי השעות ויראו בהם העתידות במשפט המזלות וזה יתכן בדבר לבן אבל בדבר מיכל הוא קשה לפרש למה שמה אותם במטה מקום דוד ואותו הכלי אינו בתכונה הזאת והחכם ראב"ע זכרו לברכה כתב כי התרפים הם על צורת בן אדם והיא עשויה לקבל כח עליונים והעד שהתרפים כן התרפים ששמה מיכל במטה עד שחשבו שומרי הבית שהם דוד:
Regarding the Terafim, some say they are idols, like the Terafim of Lavan which Rochel stole, and Lavan was an idol worshiper, like he said: "Why did you steal my gods?" (Genesis 31:30). However, heaven forbid that there should be idols in the house of Dovid. Some instead say that Terafim are a bronze vessel used to tell time and to know the future using astrology. This makes sense for Lavan, but for Michal why would she place them in Dovid's bed? This vessel shouldn't be in the shape [of a man]. The Sage Ibn Ezra of blessed memory explains that the Terafim are in the shape of a man, and are used to receive the strength of the upper [forces]. The proof for this is the palace guards thought it was Dovid.
So there seems to be a dispute about the purpose and nature of the Terafim. JPS for whatever reason chose to translate it as idols, but other translations, due to the obvious question involved, chose the other explanations. It would appear the explanation of predicting the future or "receiving the strength of the upper [forces]" isn't a halachic problem for the Radak, although I'm not sure why.
Interesting to note that some explain the Terafim as a mixture of the different explanations: an idol in the shape of a human. Or, more accurately, the head of a human. See here. Obviously if this were the Terafim of Dovid, your question is still unresolved.
All translations are my own. All quotes are the header word תרפים in some conjugation, except where noted, and all quotes are to Bereishis 31:19, except where noted. I go through the sources here; if you don’t want to see all of them, scroll all the way to the bottom for a summary.
Metzudas Tzion to our passuk in Shmuel is of the opinion that Teraphim weren’t always made to be idols:
הם העשויים בצורת אדם, מהם לעבודה זרה, ומהם לצורת אדם ידוע, והנשים היו עושות על צורת בעליהן, להסתכל בתארו מרוב האהבה:
They were made in the figure of a man, some for idol worship, and some in the image of a specific person. The women would make them in the image of their husbands, to look at his form from an abundance of love.
This seems to be Rashi’s understanding as well, as he translates the word in Shmuel as
עשוים בדמות גוף אדם
made in the likeness of a human body
in spite of translating it as an idol in Bereishis, where he explains that Rachel stole her father’s teraphim because
להפריש את אביה מעבודה זרה נתכוונה
she intended to separate her father from idolatry.
The Radak to Shmuel quotes the understanding that they are idols, but then, on the grounds that c”v David HaMelech would have an idol in his house, gives a second explanation:
ויש אומרים שהוא כלי הנחשת העשוי לדעת חלקי השעות ויראו בהם העתידות במשפט המזלות
Some say that they are copper vessels made to know the division of the hours, and to see with them the future through astrology.
The idea seems to be that one could use the device to see the night sky on a future date, and, seeing where the stars land, can predict the future much farther in advance than one would normally.
I find it interesting that the problem the Radak has with this interpretation is not that the original problem - how could David have an idol?! - still stands - how could David try to predict the future when that’s also forbidden?! - but rather, his problem is that such a device doesn’t belong in a bed, so why was Michal putting it there?
Therefore he turns to the Ibn Ezra’s approach. While the Radak had no problem with the Teraphim being an astrological clock in the context of Lavan, the Ibn Ezra wasn’t willing to say that. While he doesn’t really explain his problem, he doesn’t really explain his solution, either:
והקרוב אלי שהתרפי' הם על צורת בני אדם והיא עשויה לקבל כח עליונים ולא אוכל לפרש.
It seems closer to me that the Teraphim were [formed] according to the figure of a person, and it was made to accept the power of the Heavens. I am unable to explain.
Well, isn’t that convenient (sarcasm intended). Nevertheless, he does prove his assertion - at least, that it’s in the form of a person - from the fact that Michal stuck it in the bed.
At the very end of his piece he rejects Rashi’s opinion that she took them to stop her father from serving idols, on the grounds that she would have buried them rather than take them with her. Therefore he explains the passuk by Lavan in the above vein:
והקרוב שהיה לבן אביה יודע מזלות ופחדה שאביה יסתכל במזלות לדעת אי זה דרך ברחו
The closer [approach] is that her father Lavan knew astrology, and she was afraid that her father would gaze at the stars to know on which road they fled.
At first glance I read this piece as a printer’s error, and it should be earlier on, when the Ibn Ezra is still entertaining the idea that it’s an astrological clock. But perhaps the Ibn Ezra understands that Lavan knew how to “tap into” the heavenly influence on his Teraphim for them to guide him. I’m not exactly sure.
Pirkei d’Rebbi Eliezer 36:14 brings down a, um, creepier understanding of the Teraphim:
ומה הם התרפים, שוחטין אדם בכור ומולקין את ראשו ומולחין אותו במלח ובשמן טוב וכותבין על טס זהב שם רוח טומאה ומניחין אותו בכר ומדליקין נרות לפניו ומשתחוין לו והוא מדבר עמהן.
What were the Teraphim? They would slaughter a firstborn human, cut his head off, and salt him with salt and good oil, and they would write the name of a spirit of tumah on a golden placard. They would place him on a mattress, light candles before him, and prostrate to him, and he would speak with them.
This Midrash also appears in Tanchuma Vayeitzei 12.
This is a disturbing Midrash, but it also leaves the question of what Michal was doing with one. After all, in this version, the Teraphim are actual human beings killed for literal demonic purposes - not a figurine that someone made. Plus, Rachel’s not schlepping a dead body, nor could Yaakov not know that she was after three days. The Midrash doesn’t leave us any hints, but Targum Yonasan does. He quotes the Midrash with a very important addition:
וּגְנֵיבַת רָחֵל יַת צַלְמָנַיָא דַהֲווֹן נַכְסִין גַבְרָא בּוּכְרָא וְחִזְמִין רֵישֵׁיהּ וּמַלְחִין לֵיהּ בְּמִילְחָא וּבוּסְמָנִין וְכָתְבִין קוּסְמִין בְּצִיצָא דְדַהֲבָא וִיהָבִין תְּחוֹת לִשְׁנֵיהּ וּמְקַיְמִין לֵיהּ בְּכוּתְלָא וּמְמַלֵיל עִמְהוֹן וְאִילֵין הֲווֹן דַהֲוָה גָחִין לְהוֹן אָבוּהָא
And Rachel stole his figurines. For they would slay a firstborn man, cut off his head, salt him with salt and spices, write an incantation on a golden head-plate which they put under his tongue, and they stood him against the wall, and he would speak to them. It was to this that her father bowed.
There are a few minor differences, like what it was they put on the piece of gold, but I’d like to highlight that according to Targum Yonasan, there were the Teraphim themselves, and there were the bodies used. It was the former which Rachel stole, and which Michal had. In this version, it’s not dissimilar from the Metzudas Tzion’s and Rashi’s understanding, except that they discuss idolatry whereas this Midrash discusses divination.
The Ramban attacks Rashi. Unlike my earlier reading of Rashi, Ramban sees him as claiming that all Teraphim are idols. Being left with the problem that David couldn’t have idols in his house, he poses the earlier theory of the astrological clock, and defends it. Because of its length, I will not translate the whole piece here; suffice it to say that he demonstrates this both etymologically and from context literally anywhere the word appears.
והמלה נגזרת מלשון רפה ידים (שם ב יז ב) נרפים אתם נרפים (שמות ה יז) יקראו אותם "תרפים" לרמוז בשמם כי דבורם כמו נבואה רפה תבא ברב ותכזב לעתים רחוקות כמו שאמרו (זכריה י ב) כי התרפים דברו און והנה יעשו אותם קטני אמנה להם לאלהים לא ישאלו בשם הנכבד ולא יתפללו אליו רק כל מעשיהם בקסמים אשר יגידו להם התרפים וכתוב (שופטים יז ה) והאיש מיכה לו בית אלהים ויעש אפוד ותרפים ושם כתוב (יח ה) שאל נא באלהים ונדעה התצליח דרכינו כי בתרפים היו שואלים וכן היה הענין בישראל באפוד כי אחרי אשר הורגלו באפוד הקדש עשו כדמותו והיו שואלים בו ומאמינים בדבריו ותועים אחריו גם בחלים לא ידרשו את ה' כי אם בהם וזה טעם ויעש אותו גדעון לאפוד ויצג אותו בעירו בעפרה ויזנו כל ישראל אחריו שם ויהי לגדעון ולביתו למוקש (שופטים ח כז) כי סרו מאחרי ה' והנה לבן היה קוסם ומנחש כאשר אמר (לעיל ל כז) נחשתי וארצו ארץ קוסמים מעולם כדכתיב (ישעיהו ב ו) כי מלאו מקדם ועוננים כפלשתים ובלעם בן בעור הקוסם היה מעירו וזה טעם למה גנבת את אלהי
The Malbim says similarly that the Teraphim could divine things. It’s not clear which of the previous opinions regarding divination he holds of.
ולבן. [...] ורחל גנבה את התרפים, שלא ינחש ע"י התרפים הדרך שהלך שם יעקב
“And Lavan” - [...] And Rachel stoke the Teraphim, so that he not divine through the Teraphim which way Yaakov went.
We’ve got quite a few opinions here, so let me try to summarize them.
It’s not clear to me which opinion the Malbim subscribes to, except that he clearly does not agree with #1.
Just to confuse things further, here’s from Eichah Rabbah, Pesichah §23. In context, a Bas Kol had been telling Nevuchadnetzar to go destroy the Beis HaMikdash, and for 12 years he wouldn’t. Eventually he decided to divine if he should listen or not. One of the methods he tried was that
שאל בתרפים בעבודת כוכבים שלו
he asked his Teraphim, his idols.
Perhaps none of these sources are arguing in principle. Maybe everyone agrees that the Teraphim are sometimes random statues and sometimes idols, and they simply argue in how and why they were served - Were they just idols? Did they predict the future? How?
