“I once asked abu Ja‘far (a.s.), about the words of Allah, ‘. . . during the night in Sajdah (prostration) and in standing position fearful of the next life and hopeful of the mercy of his Lord. . . .’ (20:130). He (the Imam) said, ‘It is a reference to the nightly optional Salah (prayer).’ I then said, ‘ . . . and in both ends of the day perhaps you will become happy. . .’ (20:130). He (the Imam) said, ‘It is a reference to optional Salah (prayer) during the day.’ I then said, ‘. . . when the stars go back. . . .’ (52:49). He (the Imam) said, ‘It is a reference to the two Rak‘at before the morning Salah (prayer).’ I then said, ‘. . . after Sujud (prostrations) . . .’(52:40) He (the Imam) said, ‘It is a reference to the two Rak‘at after al-Maghrib.’”