Parashas Bo · Shemos 12:7 · TT note 1
Torah Temimah on Shemos 12:7, note 1 (on וְלָקְחוּ מִן־הַדָּם) points to Mechilta.
Sefaria — Exodus 12:7
Sefaria — Torah Temimah on Exodus 12:7
Sefaria — Mechilta
English: “They shall take of the blood” — might it be by hand? Therefore it says, “And you shall dip [it] in the blood that is in the basin” — and saf means only a vessel.
Clarifying derash from the later verse: the blood for the doorposts is received in a vessel, not applied by hand from the animal.
The blood placed on the mezuzot and lintel is taken from blood collected in a vessel.