Albert Barnes on Galatians 3:27

For as many of you. Whether by nature Jews or Gentiles.

As have been baptized into Christ. Or unto εις--the same preposition which, in Gal 3:24, is rendered unto Christ. That is, they were baptized with reference to him, or receiving him as the Saviour. See this explained Rom 6:3.

Have put on Christ. That is, they have put on his sentiments, opinions, characteristic traits, etc., as a man clothes himself. This language was common among the ancient writers. Rom 13:14.

(c) "For as many of you" Rom 6:3