Sayyiduna Jabir (may Allah be pleased with him) narrates: The Prophet (peace and blessings be upon him) said: "When the iqamah is given for the prayer, the gates of the sky are opened and supplication is answered."
Imam Ahmad recorded it; its chain contains a narrator, Ibn Lahi'ah, about whom there has been criticism.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1918