The Baptism Formula — One Name Not Three
Matthew 28:19 contains a formula that the tradition reads as three names. The disciples who received that instruction baptised in one name. Under Rule 1 the disciples were not disobeying. They understood what the instruction meant.
> Matthew 28:19 — Go therefore and make disciples of all nations, baptising them in the name of the Father and of the Son and of the Holy Spirit.
In the name — singular. Not in the names — plural. One name. The Father, the Son, and the Holy Ghost each have the same name because they are three roles of the same Spirit. The name of all three is the one name above every name.
Every Recorded Baptism in Acts — One Name
> Acts 2:38 — Repent and be baptised every one of you in the name of Jesus Christ for the forgiveness of your sins.
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> Acts 8:16 — For he had not yet fallen on any of them, but they had only been baptised in the name of the Lord Jesus.
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> Acts 10:48 — And he commanded them to be baptised in the name of Jesus Christ.
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> Acts 19:5 — On hearing this, they were baptised in the name of the Lord Jesus.
Four recorded baptisms in the book of Acts. All four use the name of Jesus only. The disciples who were present when Jesus spoke Matthew 28:19 — who heard the instruction directly — immediately went and did what appears to be something different. Under Rule 1 they were not disobeying. They understood that the name of the Father and of the Son and of the Holy Ghost is Jesus. One name. Because the Father is the Spirit, the Spirit is the Word, and the Word took the name Jesus in the incarnation. Baptising in that one name is obeying Matthew 28:19 exactly as the apostles understood it.
The Eusebius Confirmation
As established in the Council of Nicaea section — Eusebius quotes Matthew 28:19 approximately eighteen times before Nicaea without the trinitarian formula. His pre-Nicaea quotations reflect the same understanding as the Acts baptisms: one name, not three. The three-name formula appears in his post-Nicaea quotations, consistent with the council ‘s insertion. The pre-Nicaea church baptised in one name. The post-Nicaea church was instructed to baptise in three. The change is traceable to 325 AD.