John 17:19

And for their sakes I sanctify myself, that they also might be sanctified through the truth.

And for their sakes I sanctify myself, that they also might (or 'may') be sanctified through the truth, [ en (G1722) aleetheia (G225)] - 'in the truth,' or 'in truth.' Since the article is wanting in the original, we may translate, as in the margin, 'that they also may be truly sanctified,' in contrast with those ritual sanctifications with which as Jews they were so familiar. So Chrysostom, Luther, Calvin, Beza, Bengel, Meyer. But since in 2 John 1:3, and 3 John 1:3, the beloved disciple speaks of "walking in [the] truth," without the article-meaning certainly not 'walking truly,' but 'walking in the truth of the Gospel'-it is much better to understand our Lord to refer here to that same truth of which he had spoken in John 17:17 as the element or medium of all sanctification. So Erasmus, Lucke, Tholuck, Alford, Lange. 'The only difference,' says Olshausen excellently, 'between the application of the same term (sanctify) to Christ and the disciples is that, as applied to Christ, it means only to consecrate; whereas in application to the disciples, it means to consecrate with the additional idea of previous sanctification, since nothing but what is holy can be presented as an offering.

The whole self-sacrificing work of the disciples appears here as a mere result of the offering of Christ.' But it should be added, in further illustration of the vast difference between the sanctification of the Master and that of the servants, that He does not say, 'I sanctify Myself through the truth,' but simply, "I sanctify Myself," that is, 'set Myself apart by Self-consecration;' and while He says of His own sanctification that it was "for their sakes," He does not say that they were to be sanctified for others' sakes-though that, in a certain inferior and not unimportant sense, is true enough-but simply, "that they also might be sanctified through the truth." Thus, in language which brings His people into the nearest and most blessed conjunction with Himself-in a common sanctification-does Jesus, by sharpest lines of demarcation, distinguish between Himself and them in that sanctification.