The sayings of the Lord are pure sayings. Rabbi Joshua ben Levi said: The Scripture established two or three expressions and did not utter anything improper. As it is said, "Of the clean animal, and of the animal that is not clean" (Genesis 7:8). Rabbi Tanchum said: The Holy One, blessed be He, spoke two expressions to you and they are pure.
To whom did He give the tribe of Levi? To the one of whom it is written, "And he shall sit as a refiner and purifier of silver" (Malachi 3:3). And which is the section that deals with the dead? The one that begins, "Speak unto the priests, the sons of Aaron, and say unto them" (Leviticus 21:1).
Rabbi Yannai said: The words of the Torah were given in concise language, but for every matter that the Holy One, blessed be He, spoke to Moses, He would speak from two aspects: one clean and one unclean. He said before Him, "Master of the Universe, until when will we stand for the purification of the law?" He replied, "After the majority, incline." The majority of the judges who rule that the unclean is unclean, and the clean is clean.
Rabbi Abbahu said in the name of Rabbi Jonathan: Rabbi Akiba had an advanced disciple who would render the unclean unclean with one expression, and the clean clean with one expression. So too did Rabbi Meir have a disciple named Sumchus, who would render the unclean unclean with one expression, and would then render it clean with one expression, as it is said, "He is pressed, he is seven times refined" (Psalms 12:7).
Rabbi Joshua said in the name of Rabbi Levi: In the days of David, even infants knew how to expound the Torah in two aspects, as it is written in Psalm 7. (source: Sotah 42a, translation adapted from sefaria.org)