What is the ruling on one who vows to pray all of his obligatory prayers in the mosque and commits to praying two rak'ahs for every obligatory prayer he does not pray in the mosque? And is this vow valid?

Prayer in the mosque is a religious requirement, and abstaining from it without a valid excuse is forbidden. Whoever vows to perform the obligatory prayers in the mosque is bound by that vow, for the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him." However, if his vow is due to obstinacy (such as saying: "If I do not pray in the mosque, then I must pray two rak'ahs"), and his intention is to prevent himself from laziness, then an expiation for a broken oath (kaffarat yamin) is sufficient for him.