مُوَطَّأُ مَالِكٍ
Muwatta Malik 390
Shortening the Prayer
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ سَعِيدَ بْنَ الْمُسَيَّبِ، قَالَ يُقَالُ لاَ يَخْرُجُ أَحَدٌ مِنَ الْمَسْجِدِ بَعْدَ النِّدَاءِ - إِلاَّ أَحَدٌ يُرِيدُ الرُّجُوعَ إِلَيْهِ - إِلاَّ مُنَافِقٌ .
Yahya related to me from Malik that he had heard that Said ibn al-Musayyab said, "It is said that no-one except a hypocrite leaves the mosque after the call to prayer, except for someone who intends to return."
Arabic/English book reference: Book 9, Hadith 59