Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) supplicated in the Mosque of al-Fath for three days: on Monday, on Tuesday and on Wednesday. On Wednesday his supplication was answered between the two prayers, and its effect was seen on his face. Sayyiduna Jabir (may Allah be pleased with him) says: Whenever a difficult and important matter befalls me, I wait for that hour, then I supplicate in that hour, and I recognise the acceptance of the supplication (that is, the effect of its acceptance becomes apparent).
Ahmad and al-Bazzar recorded it; Ahmad's narrators are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الحج / 5901