The 1953 RLDS edition omitted the conjunction but here. This change appears to be accidental since the original reading is perfectly fine. Elsewhere in the original text, there are 242 occurrences of but behold, none of which were ever reduced to behold in any printed edition (including the 1953 RLDS edition). Oliver Cowdery had a slight tendency to omit but in the manuscripts— but only momentarily. Interestingly, the first of these is an instance of but behold:
The critical text will maintain all the instances of original but behold.
Summary: Maintain in Alma 61:3 the but that the 1953 RLDS edition omitted, apparently accidentally.