Musnad Ahmad Hadith 22033

It is narrated from Mu'adh (may Allah be pleased with him) that in the early blessed period of the Prophet Muhammad (ﷺ), it was customary that if a person missed some rak'ahs, he would ask the worshippers, and they would indicate to him by gesture how many rak'ahs he had missed. Accordingly, he would first perform the rak'ahs he had missed and then join the congregation in prayer. One day, Mu'adh bin Jabal (may Allah be pleased with him) came late to the prayer; the people were in the sitting position (qa'dah) at that time, so he also sat down. When the Prophet Muhammad (ﷺ) finished the prayer, Mu'adh stood up and completed the part of the prayer he had missed. Seeing this, the Prophet Muhammad (ﷺ) said to the people: "You should do as Mu'adh bin Jabal (may Allah be pleased with him) has done."