Exodus 28:42

And thou shalt make them linen breeches to cover their nakedness; from the loins even unto the thighs they shall reach:

Cross-reference

In Exodus 20:26, the prohibition against steps to avoid nakedness is the very reason linen undergarments are required in Exodus 28:42.

Exodus 39:28 records the actual making of the linen undergarments commanded in Exodus 28:42.

Leviticus 6:10 shows the priest wearing the linen undergarment while performing duties, directly applying the command in Exodus 28:42.

Leviticus 16:4 requires the high priest to wear the linen undergarment on the Day of Atonement, consistent with Exodus 28:42.

Ezekiel 44:18 commands linen undergarments for priests, echoing the exact requirement in Exodus 28:42.