When the Gemoro quotes a possuk, why does it sometimes not quote the part which is the reason for the quote?

Question

(possibly related to Why does the Mishna misquote the Tanakh? )

When the Gemoro quotes a possuk, why does it not always quote the part which is the reason for the quote in the first place.

For example I recently learnt Shabbos 56b where the possuk in 1 Melochim 11 (14) is quoted as ויהי לעת זקנת שלמה נשיו הטו את לבבו leaving out the critical part (at least the next three words) which continues אַחֲרֵי אֱלֹהִים אֲחֵרִים וְלֹא הָיָה לְבָבוֹ שָׁלֵם עִם יְהֹוָה אֱלֹהָיו כִּלְבַב דָּוִיד אָבִיו:

This is the most recent example I have encountered. There are many others.

Answer 1

Possibly over time the manuscript writers, before the time of printing, would just quote the beginning and write "etc." to save themselves the writing effort (with the expectation that you knew what it was referring to). When the printers came to print it, they didn't bother writing out the full verse as well.

The Lubavitcher Rebbe uses that idea to explain why the Alter Rebbe's haggada has the extra posuk of וימררו instead of just ויעבידו - because the manuscript had ויעבידו וגו' בפרך, and the printer didn't realize that the next verse also ends with the same word, whereas the Alter Rebbe learned that specifically the next verse was the point (as the first בפרך could mean בפה רך and thus not emphasize the point).

All of that to show the possibility that manuscript writers could take advantage of the reader's knowledge of Tannach to save themselves some pen strokes.