It is narrated from Ibn Abi Mulaykah; he said: Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) was asked about the children (of the polytheists): will they be in Paradise? He said: "It is enough for you to know that this very matter is what Sayyiduna Musa and al-Khadir (peace be upon them both) disagreed about." The chain of narration of this hadith is sahih (authentic), but the two Shaykhs (Bukhari and Muslim) did not record it.