First, by its own admission, the NWT is a translation of the Wescott and Hort Greek text. However, in Acts 5:31, there is no difference between W&H vs any other such as UBS5, NA28, Byzantine text and TR etc. UBS5 shows no variations in the text at Acts 5:31. NA28 does list some minor variants but none that changes the sense and all MSS have the same word ἀρχηγός (archégos).
The operative word here is ἀρχηγός (archégos) which occurs just four times in the NT in Acts 3:15, 5:31, Heb 2:10, 12:2. In all these cases, the NWT translates ἀρχηγός (archégos) as "chief agent", presumably to fit its predetermined theology.
I could find no reputable lexicon to support such a translation. Here are some lexicons:
- Thayer: Chief leader, prince, author
- NAS: author, prince
- BDAG: (1) one who has a preeminent position, leader, ruler, prince; (2) one who begins or originates something that is first in a series, instigator; (3) one who begins or originates, originator, founder.
- Souter: originator, author, founder
- Newman: leader, pioneer, founder, founder, originator
- RGNT(NIV): leader, ruler, prince, originator, founder
- Friberg, Friberg, Miller (ANLEX): (1) strictly, one who goes first on the path, hence, leader, prince, pioneer; (2) as one who causes something to begin originator, founder, initiator
ἀρχηγός (archégos) is constructed of two Greek words: ἀρχή (arché) + ἄγω (agó) = chief/prince + to lead; hence chief leader, or originator, etc.
It appears the NWT prefers "chief agent" to fit with their Arian theology that Jesus is never an originator/author but only an agent of God's will.
In commenting on Acts 3:15 ("And killed the Prince of life ..."), Ellicott observes:
(15) And killed the Prince of life.—The word translated “Prince” is
applied to Christ here and in Acts 5:31. In Hebrews 2:10 we meet with
it in “the Captain of their salvation;” in Hebrews 12:2, in “the
Author and Finisher of our faith.” Its primary meaning, like that of
prince (princeps), is one who takes the lead—who is the originator of
that to which the title is attached. The “Prince of life,” the
“Captain of salvation,” is accordingly He who is the source from which
life and salvation flow. In the LXX. of the Old Testament it is used
for the “chieftains” or “princes” of Moab and the like (Numbers 13:3;
It is significant that John labors the point that Christ is not the agent of life and light but the actual source of life and light in places like John 1:4, 3:36, 8:12, 14:6, 1 John 1:2, 5:11, 12, etc.
Matthew Poole observes (in commenting on Acts 3:15):
The Prince of life; as God, he is the Author of our temporal life too,
in whom we live, and move, &c., and in whose hand is our breath; but
Christ, as Mediator, is the guide and way to eternal life, John 14:6.
These are said to have killed our Saviour, though neither Herod, nor
Pilate, nor probably many (if any) of them that nailed him to the
cross, were present; but it was done for their sakes, and at their
desires, and therefore by their means; and it is here charged upon
them, as done by them.