כִּ֚י אִם־בֹּ֣א אַתָּ֔ה עֲשֵׂ֖ה חֲזַ֣ק לַמִּלְחָמָ֑ה יַכְשִֽׁילְךָ֤ הָֽאֱלֹהִים֙ לִפְנֵ֣י אוֹיֵ֔ב כִּ֥י יֶשׁ־כֹּ֛חַ בֵּאלֹהִ֖ים לַעְז֥וֹר וּלְהַכְשִֽׁיל׃
Pero si tú vas, si lo haces, y te esfuerzas para pelear, Dios te hará caer delante de los enemigos; porque en Dios está la fortaleza, ó para ayudar, ó para derribar.
Rashi on II Chronicles
But if you come The meaning is: If you do not believe my words, will you not try [to put effort into your military campaign?] Come, do, and strengthen yourself for war.
Rashi on II Chronicles
to help or to cause to stumble The meaning is: He has the strength to help you without the army of Ephraim and to cause you to stumble if you take them with you.