A.T. Robertson Commentary John 14:16

"And I will pray the Father, and he shall give you another Comforter, that he may be with you for ever," — John 14:16 (ASV)

And I will pray the Father (καγω ερωτησω τον πατερα). Ερωταω for prayer, not question (the old use), also in 16:23 (prayer to Jesus in same sense as αιτεω), 26 (by Jesus as here); 17:9 (by Jesus), "make request of."

Another Comforter (αλλον παρακλητον). Another of like kind (αλλον, not ετερον), besides Jesus who becomes our Paraclete, Helper, Advocate, with the Father (1 John 2:1, Cf. Romans 8:26f.). This old word (Demosthenes), from παρακαλεω, was used for legal assistant, pleader, advocate, one who pleads another's cause (Josephus, Philo, in illiterate papyrus), in N.T. only in John's writings, though the idea of it is in Ro 8:26-34. Cf. Deissmann, Light, etc., p. 336. So the Christian has Christ as his Paraclete with the Father, the Holy Spirit as the Father's Paraclete with us (John 14:16,26; 15:26; 16:7; 1 John 2:1).

For ever (εις τον αιωνα). This the purpose (ινα) in view and thus Jesus is to be with his people here forever (Matthew 28:20). See 4:14 for the idiom.