1 Samuel 21:6
So the priest gave him hallowed bread: for there was no bread there but the shewbread, that was taken from before the LORD, to put hot bread in the day when it was taken away. So the priest gave him hallowed bread: for there was no bread there but the shewbread, that was taken from before the LORD, to put hot bread in the day when it was taken away.
No common bread was present, so the priest gave David the hallowed shewbread that had been taken from before the Lord, to satisfy his hunger. That bread was ordinarily reserved for the priests alone, and on the day it was taken away fresh hot bread was put in its place. David received the sacred bread of the tabernacle when hungry and shared it with his hungry followers.
Because of his hunger his eating was guiltless, showing that meeting urgent human need may take precedence over a ceremonial restriction on sacred things, especially when done in service to God. Jesus used this example to uphold the right of the disciples to gather grain for food on the Sabbath, showing that service to God and His redemptive purpose are central to Sabbath observance. Meeting hunger takes precedence over restrictive rules about sacred things, and meeting a genuine human need can be right even when it involves something sacred.
The exceptional granting of the holy bread in a case of need parallels the use of tithe funds in a needful case, which does not excuse carelessness or laxity in paying tithe. David deceived the priest about why he had come, showing lack of faith in God, and this led to the high priest's death.