Shar' man qablana (the law of earlier prophets, and whether it binds us)

In language shar', shari'a and shir'a are the clear road down to water. In the technical sense shar' is the religion God established for His servants and commanded them to follow. 'Those before us' are the messengers before our Prophet to earlier peoples, and their law is what they brought before his mission. ¹

The revealed laws all come from one source and share one root in the principles of belief, such as the oneness of God, faith in resurrection, Paradise, Hell and the angels. ¹ The usulis differ on whether the Prophet ﷺ himself worshipped under the law of an earlier prophet before his mission; some say yes, some deny it. ² Where our law confirms an earlier rule it is our law; where it abrogates it, it is not our law, by agreement; where our law is silent about confirming or abrogating it, the jurists differ. ²

The Hanafis, Malikis and Hanbalis hold that it binds us when God tells it in the Qur'an without denial or endorsement, citing the verse 'follow their guidance' and the verse 'then We revealed to you: follow the creed of Abraham, a man of pure faith'. ² The sounder Shafi'i view holds it does not bind us. They cite the report of Mu'adh sent to Yemen, who was asked how he would judge and answered by the Book, then the sunna, then independent reasoning, without mention of the earlier law; the report is weakened by scholars for an unknown narrator in its chain. ³

Some jurists built rulings on the first view; for example, a dead man found in the abode of Islam who is uncircumcised and wears a girdle of the People of the Book is not buried in Muslim graves, on that sign. ³ The full treatment and the arguments of each side are in the usuli appendix. ³