Sa’ad ibn Abdillah from Ahmad ibn al-Hasan ibn Ali ibn Faddal from Amr ibn Said from Musaddiq ibn Sadaqah from Ammar al-Sabati, who said: I asked Aba Abdillah عليه السلام, peace be upon him, about a man who performs the obligatory prayer, then finds a group of people praying in congregation is it permissible for him to repeat the prayer with them? Imam عليه السلام said: “Yes, and it is better.” I said: “And if he does not do it?” Imam عليه السلام said: “There is no harm.”