ויאמרו האנשים ההמה... למה נגרע לבלתי הקריב את קרבן ד' במועדו
A group of people, who due to their being in a state of tumah, ritual impurity, were ineligible to bring the Korban Pesach, presented themselves before Moshe Rabbeinu, asking for a dispensation of some sort. Their desire to offer the Korban Pesach was so intense that they appealed to Moshe to somehow, someway, help them experience this milestone event. As a result of their burning desire to perform the mitzvah, Hashem made them agents through whom He revealed the mitzvah of celebrating Pesach Sheni, the Second Pesach. Essentially, it was to be viewed as a makeup Pesach. This is the…