451. Dua Etiquette of praising a fellow Muslim
The Prophet (ﷺ) said: "Whoever amongst you has to praise his brother should say:
أَحْسِبُ فُلَانًا وَاللَّهُ حَسِيبُهُ وَلَا أُزَكِّي عَلَى اللَّهِ أَحَدًا أَحْسِبُهُ كَذَا وَكَذَا
اَحْسِبُ فُلَانًا وَاللّٰهُ حَسِيْبُهٗ وَلَا اُزَكِّيْ عَلَى اللّٰهِ اَحَدًا اَحْسِبُهٗ كَذَا وَكَذَا
Ahsibu fulaanan wAllaahu haseebuhu wa laa 'uzakkee 'alAllaahi 'ahadan ahsibuhu kadha wa kadha
Translation
I think that he is so and so, and Allah knows exactly the truth, and I do not confirm anybody's good conduct before Allah, but I think him so and so.
It is to be said when you must ensure you have knowledge that the certain characteristic is present in that person.