If one vowed to donate the first salary and received it after six months of work, is it obligatory to donate the entire accumulated salary for six months, or only the first month's salary?

A vow of obedience must be fulfilled, for the Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him." A vow is constituted by any utterance that indicates the undertaking of an act of devotion, such as the questioner saying: "If I get a job, I will donate my first salary." What is obligatory concerning the questioner's vow is to donate the first month's salary, unless she intended to donate the first money she receives regardless of whether it is a month's salary, because a vow is based on intention.