We got female captives in the war booty and we used to do coitus interruptus with them. So we asked Messenger of Allah ﷺ about it and he said, "Do you really do that?" repeating the question thrice, "There is no soul that is destined to exist but will come into existence, till the Day of Resurrection."  

أَصَبْنَا سَبْيًا فَكُنَّا نَعْزِلُ فَسَأَلْنَا رَسُولَ اللَّهِ ﷺ فَقَالَ أَوَإِنَّكُمْ لَتَفْعَلُونَ قَالَهَا ثَلاَثًا مَا مِنْ نَسَمَةٍ كَائِنَةٍ إِلَى يَوْمِ الْقِيَامَةِ إِلاَّ هِيَ كَائِنَةٌ  

We took women captives, and we wanted to do 'azl with them. We then asked Allah's Messen- ger ﷺ about it, and he said to us: Verily you do it, verily you do it, verily you do it, but the soul which has to be born until the Day of judg- ment must be born. (Using translation from Muslim 1438c)   

أَصَبْنَا سَبْيًا فَكُنَّا نَعْزِلُ ثُمَّ سَأَلْنَا رَسُولَ اللهِ ﷺ عَنْ ذَلِكَ فَقَالَ لَنَا «إِنَّكُمْ لَتَفْعَلُونَ وَإِنَّكُمْ لَتَفْعَلُونَ مَا مِنْ نَسَمَةٍ كَائِنَةٍ إِلَى يَوْمِ الْقِيَامَةِ إِلَّا هِيَ كَائِنَةٌ» قَالَ أَبُو عَبْدِ الرَّحْمَنِ حَدِيثُ مَالِكٍ وَالزُّبَيْدِيِّ أَوْلَى بِالصَّوَابِ  

We took women captives, and we wanted to do 'azl with them. We then asked Allah's Messen- ger ﷺ about it, and he said to us: Verily you do it, verily you do it, verily you do it, but the soul which has to be born until the Day of judg- ment must be born. (Using translation from Muslim 1438c)   

أَنَّهُ أَخْبَرَهُ أَنَّهُ قَالَ أَصَبْنَا سَبَايَا وَكُنَّا نَعْزِلُ فَسَأَلْنَا رَسُولَ اللهِ ﷺ عَنْ ذَلِكَ فَقَالَ لَنَا وَإِنَّكُمْ لَتَفْعَلُونَ وَإِنَّكُمْ لَتَفْعَلُونَ وَإِنَّكُمْ لَتَفْعَلُونَ مَا مِنْ نَسَمَةٍ كَائِنَةٍ إِلَى يَوْمِ الْقِيَامَةِ إِلَّا وَهِيَ كَائِنَةٌ