Musnad Ahmad 2:166

Yahya narrated to us, Shu'bah narrated to us, Qatadah narrated to us, from Sa'id ibn al-Musayyib, from Ibn 'Umar, from 'Umar, from the Prophet, peace and blessings of Allah be upon him, who said: "The deceased is punished in his grave because of the wailing over him."