At the same time spake the LORD by Isaiah the son of Amoz, saying, Go and loose the sackcloth from off thy loins, and put off thy shoe from thy foot. And he did so, walking naked and barefoot.
Spake the Lord by Isaiah - literally, by the hand of (cf. Ezekiel 3:14).
Loose the sackcloth - the loose outer garment of coarse dark hair-cloth worn by mourners (2 Samuel 3:31) and by prophets, fastened at the waist by a girdle (Matthew 3:4; 2 Kings 1:8; Zechariah 13:4).
He did so walking naked - rather, uncovered. He merely put off the outer sackcloth, retaining still the tunic, or inner vest (1 Samuel 19:24; Amos 2:16; John 21:7): an emblem to show that Egypt should be stripped of its possessions. The very dress of Isaiah was a silent exhortation to repentance.