Mat 12:3 Have you not read what David did, when he and those who were hungry?
Mat 12:4 How he entered into the house of God, and ate the offering bread, which was not lawful for him to eat, neither for them which were with him, but only for the priests?

Christ says this upon being challenged for he and his disciples picking and eating corn on the Sabbath.

"Read" is anagignôskô, which means "to know well," "acknowledge," and "to recognize." It means "read" in the sense that to read, you must recognize the characters. In this same sense, it can mean "to read aloud" or "to attend a lecture." This perhaps refers to the Jewish practice of reading the scriptures at meetings.

"Hungry" is peinaô, which means "to be hungry" or "to be starved," and it is a metaphor for desire and cravings.

"Offering" is prothesis, means "placing in public," "public notice," or "offering." "Bread" is artos, which is a cake or loaf of wheat bread. This "offering bread" (artos prothesis) refers to the twelve loaves representing the twelve tribes of Israel that was set out before the sanctuary for a week every week

"Is not lawful" is ou (not) exesti, which means "it is possible" and "it is allowed." It generally refers to something within someone's power, or, in this case with the negative, something outside of someone's power.

"Priest" is hiereus, which means a "priest" and specifically a person that offers sacrifices.

Christ is saying something very important here. He is saying that the physical demands of the body take precedence over the cultural and social demands of religion. Christ's differentiates between physical reality, which is from the Father and social cultural practices, which are never perfect because it is interpreted by flawed humans. There are different levels of real. The real of the physical world and our physical needs is more a reflection of God's will than our interpretation of God's word.

With this warning, Christ is telling us that we can never put our mere interpretation of words above physical reality. However, interestingly enough, he makes this point by actually quoting scripture.