Chivalry was from its inception closely allied to Christianity. It emerged in the 12th century, in a period of the crusades and monasticism, and it lost its hold on people with the Reformation. Some historians go so far as to postulate that chivalry was intentionally developed/encouraged by the Church as a means to "tame" or "direct" the violence of fighting men. While that seems far fetched for such a secular ideal (that tolerated a great deal of illicit love!), throughout the Age of Chivalry the Catholic Church reigned unchallenged in the spiritual realm, and chivalry paid respect to her. Thus by the 13th century a vigil in a church or the dedication of a sword at the altar had become a common (though not essential) part of the knighting ceremony.
It can hardly surprise, therefore, that piety was a knightly ideal. The "perfect" knight, was a devout Christian who gave alms to the Church. Indeed, the most fundamental duty of a knight was to protect "the helpless" and "the Church." Because churchmen were not supposed to bear arms or draw blood, priests and monks, like women, children and invalids were considered the "helpless" people that knights vowed to protect.
Balian's piety is documented. In early 1187, when he was part of a delegation sent by King Guy to Count Raymond of Tripoli to try to reconcile the two. The other military members of that delegation were lured into a lop-sided battle which resulted in a massacre of the Christian knights. Balian, however, missed this debacle at the Springs of Cresson. The reason: he had stopped to hear mass and was late for the rendezvous.