Is it obligatory to postpone fasting a seven-day vow until after Eid al-Adha, or is it permissible to fast some of it before and some after, and is expiation incumbent upon the one who made the vow?

Since the days vowed for fasting are not specified, it is permissible to delay them until any time suitable for fasting. This is because delaying the fulfillment of a vow that is not restricted to a specific time is not problematic according to many scholars. Scholars of Usul (principles of Islamic jurisprudence) have differed regarding the timing of an obligatory duty (wajib): some said it is on the instant (al-fawriyyah), while most said it is on delay (al-tarakhi). It is sunnah (recommended) to hasten the fulfillment of the vow to clear one's conscience and to preemptively engage in good deeds.