Musnad Abu Ya'la al-Mawsili 155:239

Mujahid ibn Musa narrated to us, Ishaq al-Azraq narrated to us, Awf narrated to us, from Muhammad ibn Sirin, from Abu Hurayrah, from the Prophet (peace and blessings of Allah be upon him) who said: "There are no two Muslims between whom three children die who have not reached the age of puberty, except that Allah will cause them to enter Paradise by the grace of His mercy toward them." He said: "It will be said to them, 'Enter Paradise.' They will say, 'Not until our parents come.' Then it will be said to them, 'Enter Paradise, you and your parents.'"