عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ رَضِيَ اللَّهُ عَنْهُ قَالَ ذُكِرَ ذَلِكَ عِنْدَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فَقَالَ وَمَا ذَاكُمْ قَالُوا الرَّجُلُ تَكُونُ الْمَرْأَةُ تُرْضِعُ فَيُصِيبُ مِنْهَا وَيَكْرَهُ أَنْ تَحْمِلَ مِنْهُ وَالرَّجُلُ تَكُونُ لَهُ الْجَارِيَةُ فَيُصِيبُ مِنْهَا وَيَكْرَهُ أَنْ تَحْمِلَ مِنْهُ فَقَالَ فَلَا عَلَيْكُمْ أَنْ تَفْعَلُوا ذَاكُمْ فَإِنَّمَا هُوَ الْقَدَرُ قَالَ ابْنُ عَوْنٍ فَحَدَّثْتُ بِهِ الْحَسَنَ فَقَالَ فَلَا عَلَيْكُمْ لَكَأَنَّ هَذَا زِجْرٌ
It is narrated from Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) that the mention of 'azl (coitus interruptus) was made before the Noble Prophet (peace and blessings be upon him). He (peace and blessings be upon him) said: What is that? The people said: A man has a wife, she is nursing a child, so he does not like her to become pregnant; similarly, a man has a slave woman, he has intercourse with her but does not like her to become pregnant, so they wish to practice 'azl. He (peace and blessings be upon him) said: If you do this, there is no harm upon you; this is a matter of destiny. Ibn 'Awn says: I narrated this hadith to Sayyiduna Hasan, so he said: The purpose of "fa la 'alaykum" is to rebuke for practicing 'azl.