What is the ruling on one who vowed to perform the night vigil (Qiyam al-Layl) in exchange for concealment from a sin he committed at the beginning of his puberty?

The jurists differed on whether a vow (wa'd) of a good deed (qurbah) is considered a nadhr (vow) or not. The more prevalent view is that if one intended it merely as a promise, then it is a promise and not a binding nadhr. However, if one intended it as a nadhr, then it becomes a binding nadhr that must be fulfilled upon the realization of its conditions. If it is considered a nadhr, then it is obligatory to fulfill it, due to Allah's praise for those who fulfill their vows and the command of the Prophet, peace and blessings be upon him, to do so.