Its a sort of "married to the church and the kingdom of heaven" thing. Taking a wife or concubine would effectively be cheating on god. Not that I buy it, but there it is. There are some verses in Timothy and Corinthians (they escape me at the moment) that formed the basis of the practice in roman catholic clergy and it's been carried over into other (though not all) denominations. Interesting side note, lifelong celibacy is forbidden in islam, and only married men are called to be bishop in the mormon tradition.
I am the Infantry. I am my country’s strength in war, her deterrent in peace. I am the heart of the fight… wherever, whenever. I carry America’s faith and honor against her enemies. I am the Queen of Battle. I am what my country expects me to be, the best trained Soldier in the world. In the race for victory, I am swift, determined, and courageous, armed with a fierce will to win. Never will I fail my country’s trust. Always I fight on…through the foe, to the objective, to triumph overall. If necessary, I will fight to my death. By my steadfast courage, I have won more than 200 years of freedom. I yield not to weakness, to hunger, to cowardice, to fatigue, to superior odds, For I am mentally tough, physically strong, and morally straight. I forsake not, my country, my mission, my comrades, my sacred duty. I am relentless. I am always there, now and forever. I AM THE INFANTRY! FOLLOW ME!