Regarding Saying "Mabrook" and the Correct Way to Invoke For Blessings Upon Someone
From Shaykh Ubayd aj-Jaabiree’s Explanation of the Three Fundamental Principles : page 113-114:
“It is allowable to make a supplication for a person that they be blessed.
The correct way to do this is to say: ‘Baaraka Allaahu laka‘ or ‘Baarka Allaahu ‘alayka‘ and ‘hadhal amr mubaarak‘.
The expression that is common upon the tongues of the general people is ‘Mabrook ‘ala fulaan‘ (may so and so be knelt upon); this is a blatant mistake and in opposition to the correct usage of the word in the Arabic language.
Mabrook comes from the verb Baraka and Mubaarak comes from the verb Baaraka, so don’t use the word Mabrook; alternatively, use Mubaarak because it comes from Baaraka as we stated. The common people don’t intend by their saying: ‘Mabrook alayhi’ to supplicate that this person be knelt upon, but this expression is incorrect, as they want to make a supplication for the person that they be blessed. So it is said ‘Baaraka Allaahu alayka’… and ‘Az-Zawaaj Mubaarak’ (Allaah willing, the marriage will be blessed).”