Interesting discussion. Certainly, all early Christians believed a Christian is normatively forgiven of all past sins at the moment of water baptism.
However, I do not think the laying on of hands as the ordinary means of imparting the Holy Spirit can be proven to be the consensus early Christian view. You definitely see this view in the early third century with Tertullian On Baptism, Cyprian and Apostolic Traditions (attributed to Hippolytus). But you do not see it in the earlier 2nd century sources of the Didache, Justin or Irenaeus, etc. The Didache has detailed baptismal instructions with no mention of laying on of hands. Justin says Christians experience rebirth and illumination at baptism in First Apology, with no mention of laying on of hands. Odd thing to say if we are only forgiven of sins at the moment of baptism without the new birth or Holy Spirit until some subsequent ritual.
Even more striking, Irenaeus says in Proof of the Apostolic Preaching ch. 42, speaking of the new kingdom life in Christ: "For such is the state of those who have believed, since in them continually abides the Holy Spirit, who was given by Him in baptism, and is retained by the receiver, if he walks in truth and holiness and righteousness and patient endurance." I would rely on such a clear statement from Irenaeus over Tertullian and all the rest who came later.
The one odd reference to the Holy Spirit not being imparted in baptism, but rather the Apostles' laying on of hands in Acts 8, is opposite to dozens of texts attributing to baptism far more than just remission of sins and indicating a rightly baptized member is a reborn child of God. For example, it conflicts with Acts 2:38 being normative, which promises both forgiveness of sins and being filled with the Holy Spirit at baptism, and this is made to all generations far off. Titus 3:5 describes the washing of regeneration and renewing of the Holy Spirit. Not the washing of only forgiveness of past sins. And Jesus says in John 3 we are born of water and of spirit, not forgiven only of water and born of Spirit by an unmentioned laying on of hands. Paul teaches that one who does not have the Holy Spirit is not of God, so it creates an impossible contradiction to say someone is forgiven, or born again, without the Holy Spirit. Most importantly, the gospels say the Holy Spirit descended on Jesus the moment arose from the water in baptism. We do not follow Samaritans in Acts 8. We follow Jesus.
I think the same hermeneutic that leads someone to conclude that infant baptism is likely an accretion should likewise lead to the conclusion that a very awkward 3rd century belief that Christians are normatively not yet born again or filled with the Spirit until a distinct subsequent act of laying on of hands, is likewise an accretion connected to baptism.
However, I do not think the laying on of hands as the ordinary means of imparting the Holy Spirit can be proven to be the consensus early Christian view. You definitely see this view in the early third century with Tertullian On Baptism, Cyprian and Apostolic Traditions (attributed to Hippolytus). But you do not see it in the earlier 2nd century sources of the Didache, Justin or Irenaeus, etc. The Didache has detailed baptismal instructions with no mention of laying on of hands. Justin says Christians experience rebirth and illumination at baptism in First Apology, with no mention of laying on of hands. Odd thing to say if we are only forgiven of sins at the moment of baptism without the new birth or Holy Spirit until some subsequent ritual.
Even more striking, Irenaeus says in Proof of the Apostolic Preaching ch. 42, speaking of the new kingdom life in Christ: "For such is the state of those who have believed, since in them continually abides the Holy Spirit, who was given by Him in baptism, and is retained by the receiver, if he walks in truth and holiness and righteousness and patient endurance." I would rely on such a clear statement from Irenaeus over Tertullian and all the rest who came later.
The one odd reference to the Holy Spirit not being imparted in baptism, but rather the Apostles' laying on of hands in Acts 8, is opposite to dozens of texts attributing to baptism far more than just remission of sins and indicating a rightly baptized member is a reborn child of God. For example, it conflicts with Acts 2:38 being normative, which promises both forgiveness of sins and being filled with the Holy Spirit at baptism, and this is made to all generations far off. Titus 3:5 describes the washing of regeneration and renewing of the Holy Spirit. Not the washing of only forgiveness of past sins. And Jesus says in John 3 we are born of water and of spirit, not forgiven only of water and born of Spirit by an unmentioned laying on of hands. Paul teaches that one who does not have the Holy Spirit is not of God, so it creates an impossible contradiction to say someone is forgiven, or born again, without the Holy Spirit. Most importantly, the gospels say the Holy Spirit descended on Jesus the moment arose from the water in baptism. We do not follow Samaritans in Acts 8. We follow Jesus.
I think the same hermeneutic that leads someone to conclude that infant baptism is likely an accretion should likewise lead to the conclusion that a very awkward 3rd century belief that Christians are normatively not yet born again or filled with the Spirit until a distinct subsequent act of laying on of hands, is likewise an accretion connected to baptism.