What are the regular Sunnah prayers associated with the obligatory prayers?

Voluntary supererogatory prayers (nawafil) were legislated to compensate for any deficiencies in the obligatory prayers (fara’id), based on the Prophet’s (peace be upon him) saying: “Indeed, the first thing people will be held accountable for on the Day of Resurrection from their deeds is prayer… If he has voluntary prayers, [Allah] will say: ‘Complete for My servant his obligatory prayer from his voluntary prayers.’ Then, all deeds will be dealt with in a similar manner.”

Voluntary prayers are divided into absolute and restricted:

Absolute Voluntary Prayers: No specific number of rak'ahs is intended; one can conclude with one rak'ah or more. Restricted Voluntary Prayers (Sunan Rawatib): These are the voluntary prayers that follow the obligatory ones. There are different narrations regarding their number, including: Ten rak'ahs: Two rak'ahs before Dhuhr, two after it, two after Maghrib in his home, two after Isha in his home, and two rak'ahs before Fajr prayer. Four before Dhuhr and four after it. Four before Asr prayer, based on his (peace be upon him) saying: "May Allah have mercy on a person who prays four rak'ahs before Asr."

These rawatib are Sunnah (recommended) and not obligatory.