Hadith.893 - Zaid al-Shahham asked Imam Jafar ibn Muhammad Al-Sadiq (as) about a man who forgot the adhan (call to prayer) and iqamah (second call to prayer) and began the prayer.
The Imam said: "If he remembers before reciting (the Qur'an in prayer), he should send blessings upon the Prophet and his family and then recite the iqamah. But if he has already started reciting, then he should complete his prayer”.