Praying with a person praying alone as a congregation

Question: I went to the mosque and found that the congregational prayer had ended, and I found a man praying alone. Is it permissible for me to stand and pray beside him, considering him the imam and myself the follower? Please inform us, may Allah reward you.

Answer: Yes, it is permissible to pray with him according to the correct opinion of the scholars. If you catch up with a person praying alone and you have missed the prayer, there is no harm in joining him so that you pray together as a congregation; because congregational prayer is obligatory whenever possible, and it was possible in this case due to the presence of this person who is praying. So at that time, you pray with him. And Allah the Exalted knows best. The evidence for this is that the Prophet (peace and blessings be upon him)
, so this is Ibn Abbas who entered with the Prophet (peace and blessings be upon him) during the prayer. The Prophet (peace and blessings be upon him) had started the prayer alone, then Ibn Abbas joined him during it, and the Prophet (peace and blessings be upon him) approved of that. And what is permissible in voluntary prayer is permissible in obligatory prayer, unless there is evidence for differentiation or specificity. And Allah knows best.