From Sahih Muslim (Hadith 7506):
Hammam b. al-Harith reported that a person began to praise 'Uthman and Miqdad sat upon his knee; and he was a bulky person and began to throw pebbles upon his (flatterer's) face. Thereupon 'Uthman said:What is the matter with you? And he said: Verily, Allah's Messenger (ﷺ) said: When you see those who shower (undue) praise (upon others), throw dust upon their faces
Reference: Muslim 7506