The messenger of Allah (peace and blessings of Allah be upon him) said, If anyone of you is impelled to praise his brother, then he should say:
"I deem so-and-so to be so-and-so and Allah is his reckoner and I don’t praise anyone by putting the praise forward in front of Allah’s commendation, however I assume him as so and so."
…if he knows that of him.
"I deem so-and-so to be so-and-so and Allah is his reckoner and I don’t praise anyone by putting the praise forward in front of Allah’s commendation, however I assume him as so and so."
…if he knows that of him.
Sources:
Bukhari No# 2662; Muslim No# 3000