Reference for Kiddushin 141:1
מטהר שבטים שבטו של לוי מטהר תחילה שנא' (מלאכי ג, ג) וישב מצרף ומטהר כסף וטיהר את בני לוי וזיקק אותם כזהב וככסף והיו לי"י מגישי מנחה בצדקה
purifies the tribes, He will first purify the tribe of Levi, for it is said: And he shall sit as a refiner and p of silver, and he shall purify the sons of Levi, and purge them as gold and silver; and they shall offer unto the Lord offerings in righteousness.<span class="x" onmousemove="('comment',' Mal. III, 3.');"><sup>1</sup></span> R'Joshua B'Levi said: Money purifies mamzerim,<span class="x" onmousemove="('comment',' By means of their wealth they intermarry with Israel, and having thus mingled, they will not be separated in the future.');"><sup>2</sup></span> for it is said. And he shall sit as a refiner and purifier of silver.<span class="x" onmousemove="('comment',' I.e., those who married by means of their silver, He will purify by retaining them in Israel.');"><sup>3</sup></span>
Jerusalem Talmud Yevamot
In the Babli, Qiddushin 70b, the same verse is used to declare that the tribe of Levi is cleansed of bastards first of all the tribes.. What is the reason? “203Mal. 3:3. The refiner will sit, the purifier of silver, and will refine them,” etc. Rebbi Ze‘ira said, like a man who only drinks from a clean cup. Rav Hoshaia said, because we are Levites, should we lose? Rebbi Ḥanina the son of Rebbi Abbahu said, also in the future, the Holy One, praise to Him, will deal with them charitably. What is the reason? “203Mal. 3:3. They will be for the Eternal presenters of an offering in charity.”