Mukhtasar Bukhari (Abridged) 696 — Regarding children of polytheists

Narrated Abdullah bin Abbas (may Allah be pleased with them): The Messenger of Allah (peace and blessings of Allah be upon him) was asked about the children of the polytheists (if they die before reaching puberty, will they go to Paradise or Hell?). He (peace be upon him) replied: "Allah knows best, from the moment He created them, how they would have acted (if they had lived)—whether they are deserving of Paradise or Hell."