וַיְהִ֖י בַּשָּׁנָ֣ה הַשְּׁלִישִׁ֑ית וַיֵּ֛רֶד יְהוֹשָׁפָ֥ט מֶֽלֶךְ־יְהוּדָ֖ה אֶל־מֶ֥לֶךְ יִשְׂרָאֵֽל׃
Y aconteció al tercer año, que Josaphat rey de Judá descendió al rey de Israel.
Rashi
And he went down at the end of years And in I Kings (22:2) it is written: “And it was in the third year, that Jehoshaphat came down, etc.” This refers to the third year since he had released Ben Hadad (ibid. 20:34).