Exodus 20:26 - Joseph Benson’s Commentary on the Old and New Testaments

Neither shalt thou go up by steps unto mine altar Indeed afterward God appointed an altar ten cubits high. But it is probable they went not up to that by steps, but by a sloping ascent. The garments worn in those countries, being perfectly loose, were easily blown aside, so as to discover the lower parts of the body; to prevent, therefore, this inconvenience, and that no indecency might be intermixed with the service of God, this precaution was necessary. And for the same reason the priests were afterward appointed to wear breeches, which were worn by none of the people besides, Exodus 28:42.