What is a vow (nadhr) and what are its rulings, and is it permissible to change the name "Muhammad" that was vowed to be given to a newborn male, and what are the consequences of that?

A vow (nadhr) is when a Muslim obligates themselves to do something that they were not already obligated to do by Sharia. Its forms include phrases like "It is for Allah upon me." It is disliked to make vows, because the Prophet, peace and blessings be upon him, forbade them, stating that they do not avert anything but rather extract from the miserly, and because they add obligations that one may not be able to fulfill. Whoever vows an act of obedience to Allah must fulfill it, and whoever vows an act of disobedience is forbidden from fulfilling it. It is not permissible to make a vow to anyone other than Allah, the Exalted; that is polytheism (shirk). Regarding a woman's vow to name her son, she should please her husband and name her son with the name his mother chooses, because scholars differ on the validity of vows made for permissible actions. If she offers expiation for her vow, it is safer.