Matthew 12:3

“So the priest gave him the consecrated bread, since there was no bread there except the bread of the Presence that had been removed from before the LORD and replaced by fresh bread on the day it was taken away.”

This is the specific Old Testament passage Jesus references in Matthew 12:3-4.

“He entered the house of God, and he and his companions ate the consecrated bread—which was not lawful for them to do, but only for the priests?”

Direct continuation of the narrative Jesus uses to make his point.

“He answered, “Have you never read what David did when he and his companions were hungry and in need? In the days of Abiathar the high priest, he entered the house of God and ate the consecrated bread, which is lawful only for priests to eat. And he also gave some to his companions.””

Parallel account of the same event in the Gospel of Mark.

“Jesus answered them, “Have you never read what David did when he and his companions were hungry? He entered the house of God, and he and his companions ate the consecrated bread, which was not lawful for them to do but only for the priests.””

Parallel account of the same event in the Gospel of Luke.

“It belongs to Aaron and his sons, who are to eat it in a holy place, because it is a most holy part of their share of the food offerings presented to the LORD for all time.”

Provides the Old Testament law regarding who is allowed to eat the consecrated bread.