Sunan at-Tirmithiy كتاب الأضاحى باب ما جاء فى الأضحية عن الميت
ʻAlī (Ibn-Abī-Ṭālib) used to sacrifice two rams, one of them on behalf of the Prophet, peace and blessings of God be upon him, and the other for himself. He was asked about this, so he replied, "He (the Prophet, peace and blessings of God be upon him) commanded me to do this, so I shall never stop." Click on ḥadīth to read more