Not about the loins, but about the paps, or breast, as Christ and his ministers are represented, Revelation 1:13. The linen breeches are here omitted, because they were put on privately before they came to the door of the tabernacle, where the other things were put on.
Related Commentaries of Exodus 29:5
Exodus 29:5
5 And thou shalt take the garments, and put upon Aaron the coat, and the robe of the ephod, and the ephod, and the breastplate, and gird him with the curious girdle of the ephod: