Leviticus 7:13

Besides the cakes, he shall offer for his offering leavened bread with the sacrifice of thanksgiving of his peace offerings.

Cross-reference

Leviticus 23:17 also requires leavened bread for firstfruits — parallels the leavened cakes in the thanksgiving peace offering here.

In Jeremiah 33:11, the bringers of thank offerings are mentioned as a sign of restored joy—directly linked to the thanksgiving offering described here.

Amos 4:5 Contrast

Amos 4:5 mentions offering thanksgiving with leaven — same practice as Leviticus 7:13, but Amos condemns it as empty ritual.