Sayyiduna Mutalib (may Allah be pleased with him) narrates this statement of the Noble Prophet (peace and blessings of Allah be upon him): "Nafl prayer should be performed two by two; after praying two rak‘ahs, you will sit in Tashahhud, express humility and submissiveness, and raise both your hands saying: 'O Allah, O Allah.' Whoever does not do so, (then his prayer) will be incomplete." The same narration is also transmitted from Sayyiduna Fadl bin Abbas (may Allah be pleased with him) through another chain of narration.