Ibn Masud reported, "While I was walking with the Prophet ﷺ through some cultivated land, and he was leaning on a palm stalk, we passed by a group of Jews.Some of them said to the others, "Ask him about the spirit."Others replied, "What do you want with that? He may answer you with something you will not like."But they insisted, "Ask him."So one of them stood up and asked him about the spirit. The Prophet ﷺ fell silent and gave him no answer, and I realized that revelation was coming to him. I stayed standing where I was. When the revelation had come down, he recited, "And they ask you about the spirit. Say, the spirit is from the affair of my Lord, and you have not been given of knowledge except a little" [Isra 17:85].
بينما أنا أمشى مع النبي ﷺ في حرث وهو متكئ على عسيب، إذ مر بنفر من اليهود، فقال بعضهم لبعض: سلوه عن الروح، فقالوا: ما رابكم إليه؟ لا يستقبلكم بشيء تكرهونه. فقالوا: سلوه. فقام إليه بعضهم، فسأله عن الروح. قال: فأسكت النبي ﷺ، فلم يرد عليه شيئا، فعلمت أنه يوحى إليه، قال: فقمت مكاني، فلما نزل الوحي قال: {ويسألونك عن الروح قل الروح من أمر ربي وما أوتيتم من العلم إلا قليلا}
Bukhari narrated it in the tafsir (4721), and Muslim in the description of the resurrection (2794), both from Umar bin Hafs bin Ghiyath, who said, "My father narrated to us, Amash narrated to us, Ibrahim narrated to me, from Alqama, from Abdullah bin Masud," and he mentioned it.His statement, "aseeb," refers to a palm branch stripped of its leaves.