וַיַּעֲשׂ֨וּ בְנֵֽי־יִשְׂרָאֵ֧ל הַֽנִּמְצְאִ֛ים אֶת־הַפֶּ֖סַח בָּעֵ֣ת הַהִ֑יא וְאֶת־חַ֥ג הַמַּצּ֖וֹת שִׁבְעַ֥ת יָמִֽים׃
And the children of Israel that were present kept the passover at that time, and the feast of unleavened bread seven days.
Read midrashic interpretation of II Chronicles 35:17: and classical rabbinic exegesis.