Jn 16:7 7 Nevertheless I tell you the truth; It is expedient for you that I go away: for if I go not away, the Comforter will not come unto you; but if I depart, I will send him unto you. The word expedient also conveys the meaning of [appropriate for a purpose]. The Lord Jesus Christ is giving His disciples [The Church] to know the importance of the need of the comforter, which is the Holy Spirit, to come and to assist in their commission of evangelism, not only would He aid them, but He is needed for the gathering in of the rest of the Church, the people Christ died for. The Holy Spirit was responsible to apply the saving benefits to all Christ died for, the Church, His Body. He came to regenerate all of God's elect as it was according to The Everlasting Covenant of which Christ is the Surety. Isa 59:21 As for me, this is my covenant with them, saith the LORD; My spirit that is upon thee, and my words which I have put in thy mouth, shall not depart out of thy mouth, nor out of the mouth of thy seed, nor out of the mouth of thy seed's seed, saith the LORD, from henceforth and for ever. The coming of the Spirit to regenerate is a covenant promise [Ezk 36:26-27] and blood purchased, He works by means of the Father and the Son [Jn 14:26], as this is realized we give Glory To God Triune for the Salvation of a sinner, and Thank Them for the saving Operations of the Spirit. The Holy Spirit works from the Father's decree 2 Thess 2:13 13But we are bound to give thanks alway to God for you, brethren beloved of the Lord, because God hath from the beginning chosen you to salvation through sanctification of the Spirit and belief of the truth: And the Son's redemption Gal 4:5 To redeem them that were under the law, that we might receive the adoption of sons. Rom 8:15 For ye have not received the spirit of bondage again to fear; but ye have received the Spirit of adoption, whereby we cry, Abba, Father. And so He is sent to make effective what was counseled in the Everlasting Covenant for the experimental salvation of God's people that Christ died for. To all the Father elected, all whom Christ died, the Spirit is given to them as the Spirit of promise. The Holy Spirit is the bond of union between the elect members and Christ their Head, He unites us to Christ experimentally because we have the Same Spirit He has, that is the Holy Spirit in the Head is in the members, so He works like effects for the same, if He quickens the Head as here: Rom 8:11 But if the Spirit of him that raised up Jesus from the dead dwell in you, he that raised up Christ from the dead shall also quicken your mortal bodies by his Spirit that dwelleth in you. 1 Pet 3:18 For Christ also hath once suffered for sins, the just for the unjust, that he might bring us to God, being put to death in the flesh, but quickened by the Spirit: He will also quicken the Members.. Thats why each dead spiritually elect or chosen in Christ Eph 1:4 will be quickened while dead in trespasses and sins Eph 2:1,4,5 1And you hath he quickened, who were dead in trespasses and sins; 4But God, who is rich in mercy, for his great love wherewith he loved us, 5Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved ) This is a work of the Spirit in Salvation, why it was expedient that Christ go away that He may come and begin His Saving, quickening Ministry, at this time He would mostly work in behalf of the apostles to prepare the elect to receive their word..