Albert Barnes Commentary Revelation 3:4

"But thou hast a few names in Sardis that did not defile their garments: and they shall walk with me in white; for they are worthy." — Revelation 3:4 (ASV)

Thou hast a few names even in Sardis. The word names here is equivalent to persons; and the idea is, that even in a place so depraved, and where religion had so much declined, there were a few persons who had kept themselves free from the general contamination. In most cases, when error and sin prevail, there may be found a few who are worthy of the Divine commendation; a few who show that true religion may exist even when the mass are evil. (Romans 11:4).

Which have not defiled their garments. (Jude 1:23).

The meaning is, that they had not defiled themselves by coming in contact with the profane and the polluted; or, in other words, they had kept themselves free from the prevailing corruption. They were like persons clothed in white walking in the midst of the defiled, yet keeping their garments from being soiled.

And they shall walk with me in white. White is the emblem of innocence, and is therefore appropriately represented as the color of the garments of the heavenly inhabitants. The persons here referred to had kept their garments uncontaminated on the earth, and as an appropriate reward it is said that they would appear in white garments in heaven. (Revelation 19:8).

For they are worthy. They have shown themselves worthy to be regarded as followers of the Lamb; or, they have a character that is fitted for heaven. The declaration is not that they have any claim to heaven on the ground of their own merit, or that it will be in virtue of their own works that they will be received there; but that there is a fitness or propriety that they should thus appear in heaven. We are all personally unworthy to be admitted to heaven, but we may show such a character as to demonstrate that, according to the arrangements of grace, it is fit and proper that we should be received there. We have the character to which God has promised eternal life.