Muwatta Malik · 411
Maqtu Sahih · Salim al-Hilali
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ سَعِيدِ بْنِ الْمُسَيَّبِ، أَنَّهُ قَالَ مَا صَلاَةٌ يُجْلَسُ فِي كُلِّ رَكْعَةٍ مِنْهَا ثُمَّ قَالَ سَعِيدٌ هِيَ الْمَغْرِبُ إِذَا فَاتَتْكَ مِنْهَا رَكْعَةٌ وَكَذَلِكَ سُنَّةُ الصَّلاَةِ كُلُّهَا .
Yahya related to me from Malik from Ibn Shihab that Said ibn al- Musayyab said, "Which prayer is it when you remain in the sitting position in every raka?'' Said said, "It is maghrib when you miss one raka, and that is the sunna in all the prayers