It is narrated from Abu Salamah bin Abd al-Rahman (may Allah have mercy on him) that a man came to Ibn Abbas (may Allah be pleased with him) and said: "A man has died and left a daughter and a full sister." Ibn Abbas (may Allah be pleased with him) said: "The daughter gets half and the sister gets nothing; the remainder is for the agnatic heirs ('asabah)." The man said: "Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) judged otherwise; he gave half to the daughter and half to the sister as well." Ibn Abbas (may Allah be pleased with him) said: "Do you know better than Allah?" Ma'mar said: I did not understand the reason for this, until I met Ibn Tawus and mentioned to him this hadith from al-Zuhri. Ibn Tawus said: My father informed me that he heard Ibn Abbas (may Allah be pleased with him) saying that Allah Almighty says: "If a man dies having no child and he has a sister, she will have half of what he left." [Surah al-Nisa: 176] Ibn Abbas (may Allah be pleased with him) said: "Yet you say that she gets half even if he has a child."
The Shaykh said: Here "child" means a son, the evidence for which is what has already been reported from the Prophet (peace and blessings be upon him) and also from those after him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12333