A vow should be understood as nothing more than a solemn promise or obligation.
Surely you have heard more than once about the vow of silence or the vow of celibacy.
But there are other forms of vows that were quite common in the Middle Ages. Some of them are surprising to modern people.
For example, the vow of flagellation, or, more simply, self-flagellation. Flagellants believed that one could earn forgiveness from God only by mortifying one's own flesh, so they whipped themselves to exhaustion.
Those who took this vow had no belongings, slept on straw, and did not even look at women. Flagellantism was banned in 1349.
Much less harmless is the vow of pillar-dwelling, which requires one to offer prayers on any elevated place throughout one's life.
But the Irish vow of the sailor monks seems much stranger.
The disciples who made the promise had to go to sea without water or provisions - it was believed that the Lord himself would give them everything they needed if he considered it necessary.
