Water Baptism and Communion only confers any spiritual blessing if the person partaking of it has been already saved!Yes, we are aware that people generally have reasons for what they believe and say. Please consider the following:
"Then He [the risen LORD] said to them, “These are the words which I spoke to you while I was still with you, that all things must be fulfilled which were written in the Law of Moses and the Prophets and the Psalms concerning Me.” And He opened their understanding, that they might comprehend the Scriptures.
Then He said to them, “Thus it is written, and thus it was necessary for the Christ to suffer and to rise from the dead the third day, and that repentance and remission of sins should be preached in His name to all nations, beginning at Jerusalem. And you are witnesses of these things." Luke 24:44-48 --NKJV
When the risen Lord opened the minds of the disciples to understand Scripture it wasn't the words on the scrolls that changed. So when the risen Lord told them that, "repentance and the forgiveness of sins would be preached in His name beginning at Jerusalem," the only right way to understand that and preach it is, "repent and be baptized in His name for the forgiveness of sins." It is just as Peter said on Pentecost.
Why is that the only right way to preach it? It is because of who Jesus is and what Scripture says He would do.
"Then I [the LORD GOD] will sprinkle clean water on you, and you shall be clean; I will cleanse you from all your filthiness and from all your idols. I will give you a new heart and put a new spirit within you; I will take the heart of stone out of your flesh and give you a heart of flesh. I will put My Spirit within you and cause you to walk in My statutes, and you will keep My judgments and do them." Ezekiel 36:25-27 --NKJV
Some people read that and try to look back to the law, the types, but it was pointing to the future reality. The NT demonstrates this because after Herod usurped the throne everyone and their brother was looking for the Messiah. For example, part of the questioning of John included, "Why do you baptize if you are not...?"
Three take aways from the above is that the failure to believe, teach, and confess that baptism in the name of Jesus, the LORD GOD, is for the forgiveness of sins despises and denies Christ and all that baptism into Him freely gives. The second is that the one baptism from the one Lord God for the forgiveness of sins, etc., was to be believed before, during, and after the incarnation. And the third is that it is a basis of there being no relative pronoun in Mark 16:16 which turns believed away from baptized. He who believed and was baptized shall be saved.
That is the Prophetic and Apostolic witness in this regard.