If you say the shema after Plag but before three stars are out, how much needs to be repeated after?

Question

AskMoses says

Although one can pray the Maariv before nightfall, the Shema must be repeated after the stars appear.

How many paragraphs of the Shema must be repeated, all three (i.e., all of it) or just the first? What is the halachah?

Answer 1

The Halacha is in O Ch 235 (1) Mishnah Berurah 11.

The relevant text from O Ch is

וְאִם הַצִּבּוּר מַקְדִּימִים לִקְרוֹת קְרִיאַת שְׁמַע מִבְּעוֹד יוֹם, יִקְרָא עִמָּהֶם קְרִיאַת שְׁמַע וּבִרְכוֹתֶיהָ וְיִתְפַּלֵּל עִמָּהֶם, וּכְשֶׁיַּגִּיעַ זְמַן, קוֹרֵא קְרִיאַת שְׁמַע בְּלֹא בְּרָכוֹת.

and if the congregation say Shema while it is still day, he should read it with them with the blessings and say the Amidah with them and when the time comes (three small stars visible), he should read the Shema without the blessings.

On וכשיגיע זמן קורא וכו the Mishnah Berurah says:

ודי שיקרא שתי פרשיות הראשונות כיון שהזכיר יציאת מצרים בבהכ"נ דנהי דלענין ק"ש לא יצא בזה הזמן משום דאכתי לאו זמן שכיבה הוא לענין יציאת מצרים שאנו מחוייבין להזכיר בלילה יוצא בזה הזמן [מ"א בשם תר"י] אבל בשאגת אריה האריך ומסיק דירא שמים יש לו ליזהר לקרות כל השלש פרשיות של ק"ש אחר צאת הכוכבים:

And it is enough if he reads the first two paragraphs because he mentioned the Exodus in the synagogue. Although he cannot fulfill the mitzva of Shema when he reads it early because it is not yet the time when people go to bed, he will have done his duty of remembering the Exodus at night even when he reads it early. But the Shaagas Aryeh concludes that someone who fears heaven should make sure to read all three paragraphs of the Shema after the time that the stars come out.

So the first two paragraphs must be read and someone who fears heaven should read all three.

Answer 2

I happened to get this as a "halacha yomi" email and the topic was "when davening after plag but before tzeis."

Someone who recited Shema before the proper time must repeat all three paragraphs -- Shema, V’haya Im Shamoa and Vayomer -- after the zman. He should not repeat the berachos. Preferably, one should not combine his repeated Shema with kriyas Shema al hamita, even if he usually recites all three paragraphs before going to bed. The evening Shema must be recited for the sake of the mitzvah, and the bedtime Shema is recited to keep way mazikim. Furthermore, it is not proper to specifically intend to fulfill the mitzva with the bedtime Shema since at that time people often cannot focus properly on the mitzva. According to some poskim, one should not eat before repeating Shema. (משנ"ב יא-יב; ביאורים ומוספים דרשו, 15; וראה שם, 24 ו־38)