Is paying off a debt prioritized over fulfilling a vow to donate the first salary, and does debt negate the vow? If it does not negate it, is it permissible to give the vowed donation to family and relatives in the form of gifts? And must it be immediate or can it be delayed?

A Muslim should guard his tongue from vowing, as the Prophet (peace be upon him) forbade it, and because it brings no good, but rather extracts from the miser.

Debt does not negate a vow, for both are established rights. If a Muslim owes debts to people and debts to God, such as a vow, and the debt is deferred, the vow takes precedence due to its immediate obligation. However, if the debt is not deferred, the earlier of the two takes precedence, unless the vow is for a specific thing, in which case it takes precedence.

If you designate a specific recipient for your vow, you must disburse it to that recipient, and it is not permissible to deviate from it except in cases of impossibility. If you do not specify a recipient, you may disburse it as you wish, giving preference to the poor and needy. It is permissible to spend it on poor family members and relatives. The obligation is to pay it in cash, and it is not permissible to purchase gifts with it.

Whenever you are able to fulfill your vow, you must fulfill it immediately without delay.