What is the ruling on someone who missed congregational prayer, so he prayed alone, then another congregation was established and he prayed with them; which of the two prayers is counted for him?

It is recommended for someone who prayed alone and then found a congregation to pray with them, in order to attain the virtue of congregational prayer. They have already fulfilled their obligatory prayer with their first prayer and are not required to perform another prayer. Rather, it is recommended for them to repeat it for the sake of the virtue of congregational prayer. Scholars have differed regarding what one should intend in this prayer.