Rashi on Exodus 12:41/רש"י על שמות י״ב:מ״א

1ויהי מקץ שלשים שנה וגו' ויהי בעצם היום הזה AND IT CAME TO PASS AT THE END OF THE 430 YEARS … EVEN ON THE SELF-SAME DAY — The addition of the latter phrase tells us that as soon as the predetermined end of the bondage arrived the Omnipresent did not detain them even as long as the twinkling of an eye (Mekhilta). For on the fifteenth of Nisan the ministering angels had come to Abraham to announce to him the promised birth of Isaac, and on the fifteenth of Nisan Isaac was born, and on the fifteenth of Nisan the decree “between the parts” relating to Israel’s slavery was made.