Hisnul Muslim 161

For the deceased is a child, during the funeral prayer

اللَّهُمَّ اجْعَلْهُ لَنا فَرَطاً، وَسَلَفاً، وَأَجْراً

Allaahum-maj'alhu lanaa faratan, wa salafan, wa 'ajran.

O Allah, make him for us a precursor, a forerunner and a cause of reward.