Authentic Supplication Number 118.

The Messenger of Allah  said “The length of a man’s prayer, and the shortness of his address is of the victuals of the depth of his knowledge; therefore, lengthen your prayer, and shorten your address (khutbah) for verily speech can be magical.

Reporters.
‘Al-‘Adawee said it was sound, and that it was reported by ‘Imam Muslim page 158 of volume 6.