What is the ruling on vowing to sponsor three orphans, and is it permissible to contribute only to the sponsorship due to not specifying the duration of the sponsorship?

Undertaking a vow is reprehensible, according to the preponderant opinion. However, if the condition upon which the vow is contingent is met, it becomes obligatory to fulfill it in the manner vowed, based on the statement of Imam An-Nawawi, may Allah have mercy on him: "So, if the contingent condition occurs, he is obligated to fulfill what he has committed to, and there is no disagreement on this, due to the generality of the previously mentioned authentic hadith: 'Whoever vows to obey Allah, let him obey Him.'" An orphan, in Islamic law, is one whose father died while he was young and had not reached puberty, and the description of orphanage continues until puberty. Sponsoring an orphan means taking care of his affairs and interests, including expenses, clothing, discipline, and upbringing, as mentioned by An-Nawawi. It is not permissible to merely contribute. If the sponsor intended a specific duration and finds the matter difficult, he can sponsor orphans who are nearing puberty until they reach it. If the sponsor is unable to fulfill the vow but later becomes able to do so, he is obligated to fulfill it.