Authentic Supplication Number 233.

A man started to praise one of his commanders so 'Al-Miqdad started throwing sand in his face, and he said: The Messenger of Allah  ordered us to throw sand in the faces of the eulogizers.

Reporters.
'Al-`Adawee said it was sound, and that it was reported by Imam Muslim, page 127 of volume 18; `Abu Dawood, page 153 of volume 5; Ibn Majah abbreviated, #3472; At-Tirmithi, page 73 of volume 7, and he said it was comely-sound; and Muslim also reported it through different channels.