Here in verse 25, the printer’s manuscript has “Jesus beheld them as they did pray unto him”, while the 1830 edition reads “Jesus blessed them as they did pray unto him”. The 1908 RLDS edition adopted the reading in 𝓟, but the LDS text has retained the 1830 reading.
The use of the verb bless is supported by the subsequent text that refers to Jesus’s countenance smiling upon the twelve disciples and the light of his countenance shining upon them. As David Calabro points out (personal communication), this act on the part of the Lord is directly related to the blessing that Aaron and his priestly sons were commanded to give to the children of Israel:
Both 3 Nephi 19:25 and Numbers 6:25–26 refer to the Lord’s countenance shining upon the people—and, of course, this is a blessing from the Lord. Interestingly, here in 3 Nephi 19:25 the Lord himself bestows the blessing directly upon his disciples rather than through his high priest. (It should be pointed out that this passage from Numbers 6:22–27 is cross-referenced in a footnote for 3 Nephi 19:25 in the 1981 LDS edition.)
Of course, the text gives numerous examples in 3 Nephi of Jesus beholding people (including his disciples), although the verb used is not actually behold; also note that in each case, after beholding either the twelve disciples or the multitude, Jesus speaks to them:
In each instance, the text has the same phraseology, “and (he) saith unto them”. But here in 3 Nephi 19:24–25, nothing is spoken, which makes the reading with behold unusual. Also note that later in verse 30, after praying to the Father, Jesus returns and beholds the twelve disciples still praying:
In this case there is no reference to a blessing; although there is an implication of beholding, yet once more Jesus does not speak.
One important factor to consider here is that the use of beheld in 𝓟 for verse 25 is excessively redundant; in the previous verse, Jesus has already beheld the twelve disciples praying unto him:
But this problematic reading suggests what probably happened here in 3 Nephi 19:25: namely, scribe 2 of 𝓟 replaced the unexpected blessed with beheld under the influence of the previous verse and its clear implication of beholding. Not only do we have the word behold, but there is also the statement that Jesus has already seen the disciples praying. On the other hand, it seems quite implausible that the 1830 typesetter would have mistakenly replaced beheld with the unexpected blessed. There is no nearby reference to any blessing. Moreover, this is the only time in the text where someone blesses someone else while just looking at them. As Don Brugger points out (personal communication), we expect the Lord to have used words if he had blessed the twelve disciples.
The critical text will therefore maintain the difficult 1830 reading: “Jesus blessed them as they did pray unto him”. The striking resemblance with the language in Numbers 6:25–26 argues that blessed is indeed correct here in 3 Nephi 19:25. The odds are that the original manuscript read this way, which means that scribe 2 of 𝓟 accidentally misread blessed as beheld when he copied the text from 𝓞 into 𝓟. Such an error is natural enough since Jesus was indeed beholding the disciples as they prayed.
Summary: Maintain in 3 Nephi 19:25 the 1830 reading: “Jesus blessed them as they did pray unto him”; the larger passage refers to the Lord’s countenance smiling upon the disciples as well as to the light of his countenance shining upon them; in this passage we have a direct enactment of the priestly blessing in Numbers 6:22–27.