Parashas Bo · Shemos 12:10 · TT note 2
Torah Temimah on Shemos 12:10, note 2 (on עַד בֹּקֶר) points to Mechilta.
Sefaria — Exodus 12:10
Sefaria — Torah Temimah on Exodus 12:10
Sefaria — Mechilta
English: Why does it say “until morning”? Scripture comes to set a boundary for the “morning of morning” [i.e., the start of true morning at sunrise].
Boundary derash of the doubled “morning.”
The doubled wording marks the beginning of morning at sunrise, not a later hour of the day.