Parashas Vayikra · Aliyah 1 · Passuk 3
Chabad.org — English translation + Rashi
Torah Temima points to Toras Kohanim and the related discussion of “of his own will” (Rosh Hashanah 6a / parallel sugyos).
E-Daf / Tsurras Hadaf (Rosh Hashanah 6a, size=3 where available)
PDF of the daf / source
English: “Unblemished” – just as an animal that is not unblemished is not accepted, so too any animal that does not fulfill all the stated requirements is not accepted. “He shall offer it” teaches that the court may compel him; “of his own will” teaches that they compel him until he says “I am willing.”
Balance of free will and obligation — the offering must be brought willingly even when it fulfills a vow.
A person must ultimately bring an offering willingly; yet the community may encourage and even compel the fulfillment of a vow until the person affirms that willingness, teaching both personal responsibility and communal support for spiritual commitments.