Sahih Muslim Book - 16, Hadith - 3549

وَحَدَّثَنِى أَبُو الرَّبِيعِ الزَّهْرَانِىُّ وَأَبُو كَامِلٍ الْجَحْدَرِىُّ - وَاللَّفْظُ لأَبِى كَامِلٍ - قَالاَ حَدَّثَنَا حَمَّادٌ - وَهُوَ ابْنُ زَيْدٍ - حَدَّثَنَا أَيُّوبُ عَنْ مُحَمَّدٍ عَنْ عَبْدِ الرَّحْمَنِ بْنِ بِشْرِ بْنِ مَسْعُودٍ رَدَّهُ إِلَى أَبِى سَعِيدٍ الْخُدْرِىِّ قَالَ سُئِلَ النَّبِىُّ -صلى الله عليه وسلم- عَنِ الْعَزْلِ فَقَالَ « لاَ عَلَيْكُمْ أَنْ لاَ تَفْعَلُوا ذَاكُمْ فَإِنَّمَا هُوَ الْقَدَرُ ». قَالَ مُحَمَّدٌ وَقَوْلُهُ « لاَ عَلَيْكُمْ ». أَقْرَبُ إِلَى النَّهْىِ.

It was narrated from 'Abdur-Rahman bin Bishr bin Mas'ud who attributed it to Abu Sa'eed Al-Khudri, who said: "The Prophet (s.a.w) was asked about 'Azl and he said: 'It does not matter if you do not do it, for it is only the Divine Decree (that decides)."' (One of the narrators) Muhammad said: "The words: 'It does not matter' are more likely to mean that it is not allowed."