Al-Isra 17:31

And kill not your children for fear of poverty. We shall provide for them as well as for you. Surely, the killing of them is a great sin (31)

Prohibition of killing Children

This Ayah indicates that Allah is more compassionate towards His servants than a father to his child, because He forbids killing children just as He enjoins parents to take care of their children in matters of inheritance. The people of Jahiliyyah would not allow their daughters to inherit from them, and some would even kill their daughters lest they make them more poor. Allah forbade that and said:

وَلَا تَقْتُلُوا أَوْلَادَكُمْ خَشْيَةَ إِمْلَاقٍ

(And kill not your children for fear of poverty.) meaning, lest they may make you poor in the future. This is why Allah mentions the children's provision first:

نَّحْنُ نَرْزُقُهُمْ وَإِيَّاكُمْ

(We shall provide for them as well as for you.) In Surat Al-An'am, Allah says:

وَلَا تَقْتُلُوا أَوْلَادَكُم مِّنْ إِمْلَاقٍ

(kill not your children because of poverty.)[6:151]

نَّحْنُ نَرْزُقُكُمْ وَإِيَّاهُمْ

(We provide sustenance for you and for them)[6:151] and,

إِنَّ قَتْلَهُمْ كَانَ خِطْئًا كَبِيرًا

(Surely, the killing of them is a great sin.) means, a major sin. In Two Sahihs it is recorded that 'Abdullah bin Mas'ud said: "I said, 'O Messenger of Allah, which sin is the worst?' He said,

أَنْ تَجْعَلَ لِلّهِ نِدًّا وَهُوَ خَلَقَكَ. قُلْتُ: ثُمَّ أَيٌّ؟ قَالَ: أَنْ تَقْتُلَ وَلَدَكَ خَشْيَةَ أَنْ يَطْعَمَ مَعَكَ. قُلْتُ: ثُمَّ أَيٌّ؟ قَالَ: أَنْ تُزَانِيَ بِحَلِيلَةِ جَارِكَ

(To appoint rivals of Allah when He has created you.) I asked, 'Then what?' He said, (To kill your child lest he should eat with you.) I asked, 'Then what?' He said, (To commit adultery with your neighbor's wife.)"