Musnad Ahmad 33:448

Abu Amir narrated to us, Kathir—meaning Ibn Zayd—narrated to us, Abdullah ibn Abd al-Rahman ibn Ka'b ibn Malik narrated to me, Jabir—meaning Ibn Abdullah—narrated to me, that the Prophet, peace and blessings of Allah be upon him, supplicated in Masjid al-Fath for three days: Monday, Tuesday, and Wednesday. He was answered on Wednesday between the two prayers, and the joy was recognized on his face. Jabir said: "No important, grave matter has descended upon me, except that I sought that hour, supplicated during it, and recognized the answer."