Here's what Prophet Jesus is reported to have said in John 16 (12-14) while addressing his audience:
"I have yet many things to say unto you, but ye cannot bear them now. Howbeit when he, the Spirit of truth, is come, he will guide you into all truth: for he shall not speak of himself; but whatsoever he shall hear, that shall he speak: and he will shew you things to come. He shall glorify me: for he shall receive of mine, and shall shew it unto you." John 16:12-14
Christians suppose that the Greet word parakletos is the Spirit of Truth which refers to the Holy Spirit---sometimes translated as 'comforter'. But here's what Muhammad Asad says while explaining Ahmed in 61:6:
This prediction is supported by several references in the Gospel of St. John to the Parakletos (usually rendered as "Comforter") who was to come after Jesus. This designation is almost certainly a corruption of Periklytos ("the Much-Praised"), an exact Greek translation of the Aramaic term or name Mawhamana. (It is to be borne in mind that Aramaic was the language used in Palestine at the time .of, and for some centuries after, Jesus, and was thus undoubtedly the language in which the original - now lost - texts of the Gospels were composed.) In view of the phonetic closeness of Periklytos and Parakletos it is easy to understand how the translator - or, more probably, a later scribe - confused these two expressions. It is significant that both the Aramaic Mawhamana and the Greek Periklytos have the same meaning as the two names of the Last Prophet, Muhammad and Ahmad, both of which are derived from the verb hamida ("he praised") and the noun hamd ("praise"). An even more unequivocal prediction of the advent of the Prophet Muhammad - mentioned by name, in its Arabic form - is said to be forthcoming from the so-called Gospel of St. Barnabas, which, though now regarded as apocryphal, was accepted as authentic and was read in the churches until the year 496 of the Christian era, when it was banned as "heretical" by a decree of Pope Gelasius. However, since the original text of that Gospel is not available (having come down to us only in an Italian translation dating from the late sixteenth century), its authenticity cannot be established with certainty.(Quran Ref: 61:6 )