Rashi on Genesis 21:8/רש"י על בראשית כ״א:ח׳

1ויגמל AND HE WAS WEANED — at the expiration of twenty- four months (Gittin 75b).

2משתה גדול A GREAT FEAST — it is so designated because the great men of that generation were present at it (Genesis Rabbah 53:10) — Shem, Eber and Abimelech (Tanchuma Yashan, Vayishlach 23).