For prophecy never had its origin in the human will, but prophets, though human, spoke from God as they were carried along by the Holy Spirit.
NMVFor the prophecy came not in old time by the will of man: but holy men of God-The Father spoke [as they were] moved by the Holy Spirit [Ruach HaKodesh].
OJBFor no nevu'ah was at any time brought by the ratzon HaBnei Adam (will of Man), but men being carried along by the Ruach Hakodesh spoke from Hashem.
RVFor no prophecy ever came by the will of man: but men spake from God, being moved by the Holy Ghost.
TCENTFor no prophecy ever came by the will of man, but holy men of God spoke as they were carried along by the Holy Spirit.
T4Tbecause no human beings decided to make those prophecies. On the contrary, those who spoke messages from God did that because it was the Holy Spirit who caused them to do it, and therefore the Spirit must help us to interpret/understand their meaning.