Is it permissible for one who has prayed the obligatory prayer to pray with another person with the intention of a voluntary prayer?

Question:
Honorable Shaykh, a man prayed the Fajr prayer in congregation, then another man who had missed the congregation came and asked the first man to pray a voluntary prayer with him, so that the second man would gain the reward of the congregation. What is the ruling on this?

Answer:
There is nothing wrong with that. If the people have prayed and one who missed the prayer enters, it is recommended that one of those who have prayed stand up and pray with him, based on the saying of the Messenger (peace and blessings be upon him) when a man entered after they had prayed. He said (peace and blessings be upon him): It will be a voluntary prayer for him. Yes.