In 1 Samuel 21:4-6 (NASB)
4 The priest answered David and said, “There is no ordinary bread on hand, but there is consecrated bread, if only the young men have kept themselves from women.” 5 David answered the priest and said to him, “Be assured, women have been denied to us as previously when I left and the bodies of the young men were consecrated, though it was an ordinary journey; how much more then will their bodies be consecrated today?” 6 So the priest gave him consecrated bread; for there was no bread there except the bread of the Presence which was removed from its place before the Lord, in order to put hot bread in its place on the day it was taken away.
Why couldn't the military Hebrews have matrimonial relationships while the war lasted?