John 13:6 - Coke's Commentary on the Holy Bible

Then cometh he to Simon Peter:— The word rendered then, does not imply either that Jesus came first to Peter, or that he had washed any other person before him; but is used in the same sense as the English particle now, without any respect to time or order, and only to imply that a minute detail was going to follow. There is great emphasis in the word Thou in this verse. Lord, dost THOU wash My feet? "THOU, who art the Son of God, the Messiah, and consequently the King of the Jews, shalt thou wash my feet, who am but a poor fisherman, who am thy disciple, and, what is still more degrading, an unworthy sinner?"