Brian LePort has posted on one of the different manuscript readings in Acts 20:28. For those who may be new to the topic, there are two important variants in that verse in the Greek manuscripts we have. On the one hand, manuscripts vary on reading โchurch of Godโ or โchurch of the Lord.โ On the other hand, in some manuscripts, the phrase โhis own bloodโ is worded in such a way that it can mean โthe blood of (the one who is) his own.โ (For some of the variations in the Syriac, see here).
In deciding what the original reading is likely to have been in these instances, perhaps the most important thing to consider is that there has been nothing, absolutely nothing, in Luke or Acts that has depicted Jesus as God. And so it seems safe to say that the reading โthe church of God, which he bought with his own bloodโ is not original.
In the Christology of Luke-Acts, Jesus is a human being who is empowered with the Holy Spirit during his life, and raised from the dead and exalted to heaven after the end of his life. There is no point at which Jesus is depicted as being pre-existent or the incarnation of a pre-existent entity. (In fact, the only person who makes such a claim for himself in Luke-Acts is Simon Magus).
And so this instance illustrates how a careful study of a workโs Christology can allow the textual critic to draw conclusions about the likely direction of alteration. In this case, Lukeโs wording has been changed over the course of transmission to agree with developing orthodoxy, rather than vice versa.