Crusade vow

The crusade vow (also crusading vow or crusader vow) was a solemn promise to God made before a representative of the Catholic Church legally binding oneself to undertake a crusade. The vow and its attendant privileges were among the defining features of a crusade, along with crusade indulgences.

There could be no crusade without crusaders and what made a man or woman a crusader was the making of a vow . . .

The act of making a crusader's vow was often referred to as "taking the cross", since it was normal to sew a cross onto one's garments, a practice that began with the First Crusade in 1095.