Metzudat David on Judges
And I will draw: That is to say, I will put it into his heart to come to the Kishon River.
Metzudat Zion on Judges
His army: its a matter of a huge nation. considering they killed a lot
Radak on Judges
And I will draw: He said that Sisera's astrologists saw that he would not leave that war, as he would be defeated if he came out [to it]; but the Holy One, blessed be He, drew his heart to go out. And this is [the meaning of] what He said, "And I will draw." But Yonatan translated it as ...