John 17:17

Sanctify them through thy truth
The Syriac version introduces this petition, with the appellation (aba) , "Abba, Father": and the sanctification prayed for regards the apostles, either as ministers of the word, and may intend their separation for their work and office; for which though they were sanctified or separated from their mother's womb, and by Christ when he sent them forth, yet were to have a fresh commission and unction after our Lord's resurrection, and upon his ascension to heaven; and also their qualification for it, with the truth of grace and doctrine, with holiness of heart and life, and with a preservation in the truth, by being kept faithful to it: or it may also regard them as Christians and believers, and intend a greater degree of the sanctification of the Spirit, which is imperfect in this life; for though sanctification in Christ is perfect, and so it is in the saints, as to parts, yet not as to degrees; which appears from the imperfection of faith, hope, love, and knowledge, from indwelling sin, being in the best of saints, from their necessities, from their disclaiming perfection, and their desires after it. Sanctification is a progressive work, which is carried on gradually; as is clear from the characters of regenerate ones, who are first newborn babes, then young men, and afterwards fathers in Christ; from the similes, by which it is expressed as seed which opens and grows up by degrees, and light which shines more and more unto the perfect day from exhortations to a concern for the growth of it, and prayers for it: and it is indeed continually carrying on, as may be concluded from the hand in which it is; and the progress and finishing of this work, as well as the beginning of it, are entirely the Lord's; and the way and means in which this is done, are by or through the truth of the Gospel:

thy word is truth;
it is "peculiarly" so, as the Arabic version reads it. The Gospel is here meant, and is so called on account of its original, it comes from the God of truth; and because of the concern which Christ, who is the truth, has in it, he being the author, preacher, and sum and substance of it; and because the Spirit of truth has dictated it, leads into it, qualifies men to preach it, and makes it effectual: and because it contains all truth necessary to salvation, and nothing but truth, and particularly that eminent truth, salvation alone by Christ; and because it is opposed to the law, which is but a shadow, of which the good things in the Gospel are the substance: now this is the means both of the beginning, and increasing, and carrying on the work of sanctification in the hearts of God's people, as well as of an experimental knowledge of it; and an increase of that knowledge does more and more qualify the ministers of it for their ministerial work and service, which seems here chiefly designed.