וַיְהִ֖י בַּשָּׁנָ֣ה הַשְּׁלִישִׁ֑ית וַיֵּ֛רֶד יְהוֹשָׁפָ֥ט מֶֽלֶךְ־יְהוּדָ֖ה אֶל־מֶ֥לֶךְ יִשְׂרָאֵֽל׃
And it came to pass in the third year, that Jehoshaphat the king of Judah came down to the king of 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).