What is the ministry of the Holy Spirit? Jesus said that it is to our advantage for him to return to the Father because, if he didn't, he would not be able to send the Helper - the Holy Spirit. The ministry of the Spirit is part of the New Covenant; but to understand the New Covenant, we need to understand what the Old Testament says. What we see is that if Jesus did not leave (meaning, his death, burial, resurrection and ascension), the blessings of the new covenant would remain at bay and many of the promises are yet to be fulfilled.