I heard the Messenger of Allah ﷺ as saying: Do not kill your children secretly, for the milk, with which a child is suckled while his mother is pregnant, overtakes the horseman and throws him from his horse. (Using translation from Abū Dāʾūd 3881)
سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ لَا تَقْتُلُوا أَوْلَادَكُمْ سِرًّا فَإِنَّ قَتْلَ الْغَيْلِ يُدْرِكُ الْفَارِسَ فَيُدَعْثِرُهُ عَنْ ظَهْرِ فَرَسِهِ