While the Abyssinians were playing with their spears in the presence of the Messenger of Allah ﷺ, Umar came in and reached down for some pebbles to throw at them. The Prophet ﷺ said to him, "Leave them alone, Umar."
حدثنا عبد الرزاق حدثنا معمر عن الزهري عن ابن المسيب
بينا الحبشة يلعبون عند رسول الله ﷺ بحرابهم دخل عمر فأهوى إلى الحصباء يحصبهم بها فقال له النبي ﷺ دعهم يا عمر
Its isnad is sahih. Bukhari related it in 6:68 through the narration of Hisham from Mamar, and through the narration of Abdul-Razzaq from Mamar. Muslim related it in 1:243 through the route of Abdul-Razzaq, with the same wording.Al-hasba means small pebbles.