Musnad Ahmed: Hadith 2301

Give us something that we can ask this man about. They said: Ask him about ar-rooh. Then the verse “And they ask you (O Muhammad (ﷺ)) concerning the Rooh (the spirit). Say: “The Rooh (the spirit) is one of the things, the knowledge of which is only with my Lord. And of knowledge, you (mankind) have been given only a little” [al-Isra' 17:85] was revealed. They [the Jews] said: We have been given a great deal of knowledge. We were given the Torah, and whoever is given the Torah has been given a great deal of good. Then Allah revealed the words: “Say (O Muhammad (ﷺ) to mankind): “If the sea were ink for (writing) the words of my Lord, surely, the sea would be exhausted" [al-Kahf 18:109].