Great question - there appears to be a difference of lexical opinion about how the word זָמִיר (zamiyr) should be classified. Should it be:
- זָמִיר (zamiyr - Strongs 2158) meaning singing/song as in 2 Sam 23:1, Job 35:10, Ps 95:2, 119:54, SS 2:12, Isa 24:16, 25:5, or,
- זָמִיר (zamiyr - Strongs 2159) meaning branch/pruning occurring only in SS 2:12
I note the following from the various lexicons:
- BDB is divided and lists the word twice under both headings
- Wigram's "Englishman's Hebrew Concordance of the Old Testament" uses a different classification essentially combining the two and suggesting that the meaning in SS 2:12 is "singing".
- Baker and Carpenter's "Complete Word Study Dictionary of the Old Testament" essentially implies that Strong was wrong and that #2159 should be classified as #2158, "singing".
As the OP correctly notes, most modern versions appear to agree with the standard lexicons and translate the word as "singing". So why do an isolated few (NASB, NET, ASB) render this word "pruning"?
It appears to be an attempt to accommodate the LXX and its translation τομῆς (tomes) = "pruning". This is all I can suggest as the text itself strongly suggests "singing" because of the Hebrew parallelism - note the following (my translation):
- The flowers appear on the land
- The time of singing has come
- The voice of the turtledove is heard in our land
Note the comments of Ellicott:
(12) The time of the singing—Heb., zamîr·—may mean pruning (so LXX.
and Vulg.), but parallelism requires singing-time (a meaning which
analogy will certainly allow us to give to the Hebrew word zamîr). Nor
can the correctness of our version in inserting of birds be
questioned, since from the context it is plainly “the untaught harmony
of spring,” and not the voices of men intended.
Further, if it is the time of vine blossom and flowers (V13), then the time of pruning is already past.
The only way to explain this translation of the LXX is to assume that the LXX translators worked from a slightly different Hebrew text than that which has come down to us. This is also true in hundreds of other places on the OT, so this instance is anything but unusual.