Musannaf Ibn Abi Shaybah 33417 — How many grandmothers inherit?

Al-Qasim said: A man died and left behind his two grandmothers, that is, his maternal grandmother and his paternal grandmother. Sayyiduna Abu Bakr (may Allah be pleased with him) made the maternal grandmother an heir and excluded the other. A man of the Ansar said: You have left out a woman such that, if the two grandmothers had died while their grandson was alive, he would inherit nothing from the one you have made his heir, and he would inherit from the one you have left out, being her son's son. So Sayyiduna Abu Bakr (may Allah be pleased with him) made her an heir as well and made them partners in the sixth share of the estate.