A.T. Robertson Commentary John 17:20

"Neither for these only do I pray, but for them also that believe on me through their word;" — John 17:20 (ASV)

Through their word (δια του λογου αυτων). Through the agency of conversation and preaching, blessed privilege open to all believers thus to win men to Christ, but an agency sadly limited by the lives of those who speak in Christ's name.