Musnad Ahmad 2:98

Isma'il narrated to us, from Sa'id ibn Abi 'Aruba, from Qatadah, from Salim ibn Abi al-Ja'd, from Ma'dan ibn Abi Talhah, who said: 'Umar said: "I did not ask the Messenger of Allah, peace and blessings of Allah be upon him, about anything more than I asked him about the *kalalah* (inheritance of one who leaves no direct descendants or ascendants), until he poked his finger into my chest and said: 'The verse of the summer, which is at the end of Surat an-Nisa', is sufficient for you.'"