Is it permissible for a person to pray in congregation with another person without waiting for the rest of the congregants, even though they are waiting for him?

For a person to wait for the congregational prayer is better than for him to pray with only one other person, because the reward of the congregation increases as the number of worshipers increases. This is as stated in the Hadith of Ubayy ibn Ka’b (may Allah be pleased with him), that the Prophet (peace be upon him) said: «A man's prayer with another man is purer than his prayer alone, and his prayer with two men is purer than his prayer with one man. And whatever is more than that is more beloved to Allah, the Almighty and Exalted.» It is appropriate to gently remind the person of the virtue of congregational prayer. However, if he insists on praying alone or with one other person without a valid reason, his prayer is valid. This difference of opinion should not be a cause for discord, especially since some scholars do not consider congregational prayer obligatory.