Albert Barnes Commentary Mark 12:38

"And in his teaching he said, Beware of the scribes, who desire to walk in long robes, and [to have] salutations in the marketplaces," — Mark 12:38 (ASV)

In his doctrine. In his teaching, for that is how it should be understood.

Beware of the Scribes. Be on your guard; be cautious about hearing them or following them.

Scribes. The learned men of the Jewish nation.

Which love to go in long clothing. In long flowing robes, signifying their importance, leisure, and learning.

Salutations, and so on. See Matthew 23:6-7.