Ibn Ezra on Leviticus 21:22/אבן עזרא על ויקרא כ״א:כ״ב

1THE BREAD OF HIS GOD…OF THE MOST HOLY. The showbread, the guilt offering, and the sin offering, which in comparison to the peace offerings are most holy, for the peace offerings are also holy.

2AND OF THE HOLY. The tithe and the first-born.