Parashas Vayakhel · Passuk 35:22
Torah Temimah points to classical source on this unit (verified).
English: A person who completes the intention to give can become obligated even without an explicit verbal statement, as derived from “every generous-hearted person.”
Derash connecting “generous-hearted” intention with obligation in sacred vows.
For consecrated gifts, a completed intention of giving can create an obligation even without verbalizing it.