The BECNT-Acts commentary (Darrell L. Bock, p. 630) says:
- The verse does not explicitly mention the title "Son" but rather speaks of God's giving his own to gain the church. The image implies sonship. . . Thus the acquiring of the church had as its basis a substitution of God's own for those God would bring to eternal life.
This commentary has its own translation included: (Acts 20:28) ". . . which he obtained with the blood of his own [Son]." The older NWT has "[Son]" inserted and reads exactly as the commentary except "obtained" in the NWT is "purchased." The 2006 edition of the NWT took the brackets around "Son" out.
The NAC-Acts commentary (John B. Polhill, pp.427-28) says:
- A final major problem in v. 28 is both text-critical and interpretive. It involves the final clause: "Be shepherds of the church of God, which he bought with his own blood." [The NIV rendering is used in this commentary - Bobcat] The problem is the very striking statement that God puchased the church with his own blood. The reference is surely to the atoning blood of Jesus shed on the cross. It is quite possible to denote this as "God's blood" from the perspective of sound Trinitrian doctrine, but such an expression is really quite unlike anything alse in the New Testament. [Footnote here says: "Catholic scholars seem to have less trouble with the concept of Christ's blood as "God's blood." " - Bobcat] A number of significant manuscripts read "church of the Lord," which removes the difficulty; but the reading "church of God" seems to be the more likely original reading. It is possible to argue that "God" is not the intended antecedent but rather Christ, "implicitly," but that is not likely. Another possibility, favored by many recent translations and commentaries, is to translate the final phrase "with the blood of his own," "his own" referring to Christ, God's own beloved Son. This is grammatically arguable and perhaps the best solution for those who find the reference to "God's own blood" unlikely for Paul or for Acts.
Another commentary, The Bible Knowledge Commentary, p. 414 notes:
- Nowhere does the Bible speak of the blood of God the Father. The Greek here can read "by the blood of His own," that is, His own Son.
Incidentally, the whole last phrase (tou haimatos tou idiou; literally "the blood the own") is genitive, neuter, singular. The word order differs from two instances of "his own blood" in Hebrews (tou idiou haimatos; 9:12; 13:12). The difference becomes even more interesting if, as some think, Luke is the writer of Hebrews. "His own blood" also occurs in Revelation 1:5 but the construction is somewhat different (to haimati autou), precluding comparisons. (Also John versus a possible Luke as writers.)
So you have a case where each side (Trinitarians versus Non-Trinitarians) could argue, each for his own side, and feel like they have a valid argument. The NWT Reference Bible also has an appendix discussion on the phrase on page 1580 with some of the ideas presented above. It doesn't hide the fact that the KJV rendering ("his own blood") is quite possible, although, it favors the other rendering ("blood of his own") as the preferable one, with "[Son]" in brackets added for clarification. (But now taken out, the brackets that is, in newer editions.)
The LXX also has "his own blood" at Gen 9:6; Ezekiel 18:13; 33:4, 5. The construction in Greek is similar to Revelation 1:5.
Take Care
In the WT's own Interlinear the word "son" is not in the original text and has been added and placed in brackets in the translation.