Kings III 21:23

23 And the servants of the king of Syria, even they said, The God of Israel a God of mountains, and not a God of valleys; therefore has he prevailed against us: but if we should fight against them in the plain, verily we shall prevail against them.

Kings III 21:23 In-Context

21 And the king of Israel went forth, and took all the horses and the chariots, and smote with a great slaughter in Syria.
22 And the prophet came to the king of Israel, and said, Strengthen thyself, and observe, and see what thou shalt do; for at the return of the year the son of Ader king of Syria comes up against thee.
23 And the servants of the king of Syria, even they said, The God of Israel a God of mountains, and not a God of valleys; therefore has he prevailed against us: but if we should fight against them in the plain, verily we shall prevail against them.
24 And do thou this thing: Send away the kings, each one to his place, and set princes in their stead.
25 And we will give thee army according to the army that was destroyed, and cavalry according to the cavalry, and chariots according to the chariots, and we will fight against them in the plain, and we shall prevail against them. And he hearkened to their voice, and did so.

The Brenton translation of the Septuagint is in the public domain.