Chapter on the Virtue of Children
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 3|Chapter 49
وَ فِي رِوَايَةِ اَلسَّكُونِيِّ قَالَ: نَظَرَ رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ إِلَى رَجُلٍ لَهُ اِبْنَانِ فَقَبَّلَ أَحَدَهُمَا وَ تَرَكَ اَلْآخَرَ فَقَالَ لَهُ اَلنَّبِيُّ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ "فَهَلاَّ وَاسَيْتَ بَيْنَهُمَا".
In the narration of Al-Sakooni, it is reported that the Messenger of Allah سبحانه وتعالى (peace and blessings be upon him and his family) saw a man who had two sons. The man kissed one of them and left the other. The Prophet (peace and blessings be upon him and his family) said to him, "Why did you not treat them equally?"
- Ṣaḥīḥ al-Faqīh, p. 292