Hadith 503870
Chapter 9: Shortening the Prayer - كتاب قصر الصلاة فى السفر
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ سُمَىٍّ، مَوْلَى أَبِي بَكْرٍ أَنَّ أَبَا بَكْرِ بْنَ عَبْدِ الرَّحْمَنِ، كَانَ يَقُولُ مَنْ غَدَا أَوْ رَاحَ إِلَى الْمَسْجِدِ لاَ يُرِيدُ غَيْرَهُ لِيَتَعَلَّمَ خَيْرًا أَوْ لِيُعَلِّمَهُ ثُمَّ رَجَعَ إِلَى بَيْتِهِ كَانَ كَالْمُجَاهِدِ فِي سَبِيلِ اللَّهِ رَجَعَ غَانِمًا .
Yahya related to me from Malik from Sumayy, the mawla of Abu Bakr, that Abu Bakr ibn Abd ar-Rahman used to say, "Someone who goes to the mosque in the morning or the afternoon with no intention of going anywhere else, either to learn good or teach it, is like someone who does jihad in the way of Allah and returns with booty."
Reference Muwatta Malik 503870
USC-MSA web (English) reference : Book 9, Hadith 56