He blessed the people, i.e. he heartily and solemnly prayed to God for his blessing upon them; which he did both as prophet and as their king, to whom by office it belongs, by all means, to seek his people's welfare.
Related Commentaries of 2 Samuel 6:18
2 Samuel 6:18
18 And as soon as David had made an end of offering burnt offerings and peace offerings, he blessed the people in the name of the LORD of hosts.