Deuteronómio 16:7 Comentario: Rashi, Chizkuni, Ibn Ezra & Or HaChaim

ובשלת is identical with צלי אש “roast with fire” mentioned in Exodus 12:9, for it (roasting) also comes under the term בשול “cooking” (Mekhilta).

ובשלת, the true meaning of the word בשל is: “to make something ready and fit to eat.” The author cites Genesis 40,10, הבשילו אשכלותיה ענבים, “its grape clusters had become ripe,” or Exodus 23,19: גם, לא תבשל גדי בחלב אמו "do not boil the kid in the milk of its mother,” as support.

As I have explained [comment on Exodus 12: 9], the word you will cook here denotes roasting. Compare, “they cooked the Paschal sacrifice in fire” [II Chronicles 35: 13]. Scriptures says you will cook only to indicate that it must not be eaten raw.

ופנית בבקר AND THOU SHALT TURN IN THE MORNING [AND GO INTO THY TENTS] — i.e. in the morning of the second day of the Passover week. — It teaches us that he (the pilgrim) is required to stay in Jerusalem during the night when the festival terminates (Sifrei Devarim 134:2; Pesachim 95b; Chagigah 17).