1."These are the Sons of Los! These the Visions of Eternity But we see only as it were the hem of their garments when with our vegetable eyes we view these wond'rous Visions (Milton, plate 26; Erdman 123).
(No doubt the 'Bible soaked Protestant, William Blake, got this figure from Matthew 9:20: "And suddenly, a woman who had a flow of blood for twelve years came from behind and touched the hem of His garment.")
2 "The Soldiers casting lots for Christ's Garment - A Drawing. (A Descriptive Catalog, Number X11; Erdman 548)
This came perhaps from John 19:24: "They said therefore among themselves, Let us not rend it, but cast lots for it, whose it shall be: that the scripture might be fulfilled, which saith, They parted my raiment among them, and for my vesture they did cast lots. These things therefore the soldiers did."
The robe implies similar ideas; of the 46 items here's one:
"When Urizen saw the Lamb of God clothed in Luvahs robes"(4Z 8; Erdman 373) And here's a contrary: "The red robe of terror, the crown of oppression, the shoes of contempt" (French Revolution 222; Erdman 296)
In Isaiah 61:10 the two words come together in unison: "I will greatly rejoice in the LORD, my soul shall be joyful in my God; for he hath clothed me with the garments of salvation, he hath covered me with the robe of righteousness, as a bridegroom decketh himself with ornaments, and as a bride adorneth herself with her jewels."
Speaking in general you might say that both words (garment and robe) suggest the body, the mortal dimension of someone's life. The body must die, but the spirit lives on (or comes to life in some ways of speaking).
This may seem like a pretty tiresome way to get a familiarity with Blake's thought; it's what he called the minute particulars. It may seem tiresome to the novice, but an advanced student may find great profit in browsing through Blake's works-- and the Bible.
Today in the internet we have powerful tools (concordances, editors, interpretators and commentaries) for that kind of study; it may gladden the hours, especially for an older person, who has retired from the modern race of life.