Understanding Numbers 11:25
Numbers 11:25 (KJV):
And the LORD came down in a cloud, and spake unto him, and took of the spirit that [was] upon him, and gave [it] unto the seventy elders: and it came to pass, [that], when the spirit rested upon them, they prophesied, and did not cease.
The Hebrew text states ולא יספו, which literally translates into English as, "...and they did not [prophesy] again." The word "prophesy" must be supplied according to the immediate context from the preceding phrase.
Here is Gesenius' excerpt on the verb yasaf:
See Kal (3)(c), at the end, before the paragraph "Note." Gesenius writes:
Num. 11:25, "...and when the Spirit came upon them, they prophesied, but (from that day) never any more," as is well rendered by the LXX and Syr[iac].
The LXX has καὶ οὐκέτι προσέθεντο which translated as "and they no longer continued [to prophesy]." See LSJ on προσέθεντο, sec. III (5).
Is there any grammatical and linguistic justification for the translation of the KJV?