Rashi on Exodus 28:40/רש"י על שמות כ״ח:מ׳

1ולבני אהרן תעשה כתנת AND FOR AARON’S SONS THOU SHALT MAKE INNER GARMENTS — these four garments and no more; viz., the three mentioned in this verse, — the inner garment, the girdle and the מגבעות which are identical with what is elsewhere called the mitre, — and the breeches prescribed later in this section (v. 42).