Final answer:
David and those with him were not meant to eat the showbread because it was holy bread reserved for priests. An exception was made by the priest Ahimelek due to David's urgent need, demonstrating that human need could sometimes supersede ceremonial law.
Step-by-step explanation:
David and those with him were not supposed to eat the showbread, or the bread of the Presence, which was placed on the table in the Tabernacle or Temple of God. This bread was considered holy and was reserved specifically for the priests to consume, as described in Leviticus 24:5-9. Eating the showbread was a privilege and duty designated to the priests, and it represented a portion eaten in a holy place as a most holy part of the offerings made to the Lord by fire.
In 1 Samuel 21:1-6, David, who is fleeing from King Saul, and his men eat the showbread after the priest Ahimelek gives it to them because there was no other food available. This action was typically not permitted for anyone who was not a priest, but it was made an exception by the priest on the grounds of necessity and urgency. The principle demonstrated here is that human need, in some cases, could override ceremonial law.