I was walking with the Prophet ﷺ through a cultivated field in Madinah, and he was leaning on a palm-leaf stalk. He passed by a group of Jews, and some of them said to one another, "Ask him about the soul."Others said, "Do not ask him."But they asked him about the soul, saying, "Muhammad, what is the soul?"He stood still, leaning on the stalk, and I realized that revelation was descending upon him. Then he recited, "And they ask you about the soul. Say, the soul is from the affair of my Lord, and you have not been given of knowledge except a little" [Isra 17:85].Then some of them said, "We told you not to ask him."
حدثنا وكيع حدثنا الأعمش عن إبراهيم عن علقمة
كنت أمشي مع النبي ﷺ في حرث بالمدينة وهو متكئ على عسيب قال فمر بقوم من اليهود فقال بعضهم لبعض سلوه عن الروح قال بعضهم لا تسألوه فسألوه عن الروح فقالوا يا محمد ما الروح فقام فتوكأ على العسيب قال فظننت أنه يوحى إليه فقال {ويسألونك عن الروح قل الروح من أمر ربي وما أوتيتم من العلم إلا قليلا} قال فقال بعضهم قد قلنا لكم لا تسألوه
Its isnad is sahih. Ibn Kathir quoted it in the Tafsir 5:226–227 from this very place, saying, "This is how Bukhari and Muslim narrated it, from the hadith of Amash, through him." See also 2309.