How a Muslim should praise another Muslim
 

231. If any of you praises his companion then let him say:

أَحْسِب - فُلاَنَا - واللهُ حَسٍيْبُهُ

'Ahsibu fulaanan wallaahu haseebuhu

I consider (such and such a person), and Allah is his Assessor

And/Or:

وَلاَ أُزَكِّي عَلَى اللَّهِ أَحْدًا

Wa laa 'uzakkee 'alallaahi 'ahadan

I cannot claim anyone to be pious before Allah.

If you know of this (good character trait in the person) to be such and such (saying what you thinks is praiseworthy in that person).

Reference: Muslim 4/2296.