Muslim

It will be said to him: If your reason for weakening the report and abandoning argument by it is the possibility of irsal (disconnection) in it, then it is necessary for you not to affirm any mu‘an‘an isnad (chain with ‘an‘anah), until you see in it the explicit mention of hearing from beginning to end. That is because the hadith that comes to us with the isnad of Hisham ibn ‘Urwah, from his father, from Aisha, we know with certainty that Hisham heard from his father, and that his father heard from Aisha, just as we know that Aisha heard from the Prophet, peace and blessings be upon him. Yet it is possible, if Hisham does not say in a narration he relates from his father, “I heard” or “he informed me,” that there could be between him and his father in that narration another person who informed him from his father, and he did not hear it himself from his father, when he wished to narrate it mursal (disconnected) and not attribute it to the one he heard it from. And just as this is possible in Hisham from his father, it is also possible in his father from Aisha. Likewise, every isnad of a hadith in which there is no mention of hearing of some from others, even if it is generally known that each of them has heard much from his companion, it is permissible for each of them to descend in some narration and hear from someone else from him some of his hadiths, then narrate it mursal from him sometimes, without naming the one he heard it from, and sometimes he is active and names the man from whom he took the hadith and abandons irsal.