A.T. Robertson Commentary John 19:26

"When Jesus therefore saw his mother, and the disciple standing by whom he loved, he saith unto his mother, Woman, behold thy son!" — John 19:26 (ASV)

His mother (την μητερα). Common Greek idiom, the article as possessive.

Standing by (παρεστωτα). Perfect active (intransitive) participle of παριστημ, vivid and picturesque scene. The dying Saviour thinks of the comfort of his mother.

Whom he loved (ον ηγαπα). Imperfect active. Surely John is justified in inserting this phrase here. If John were his cousin, that helps explain why Jesus turns the care of his mother over to him. But the brothers of Jesus are not present and disbelieved his claims. John is the only one of the apostles with courage enough to take his stand with the women by the Cross. There is no disrespect in the use of "Woman" (Γυνα) here as there was not in 2:4. This trust is to John, though Salome, John's own mother, was standing there.