Talmud for Pirkei Avot 3:18
רַבִּי אֱלִיעֶזֶר בֶּן חִסְמָא אוֹמֵר, קִנִּין וּפִתְחֵי נִדָּה, הֵן הֵן גּוּפֵי הֲלָכוֹת. תְּקוּפוֹת וְגִימַטְרִיאוֹת, פַּרְפְּרָאוֹת לַחָכְמָה:
R. Eliezer ben Chisma says: Kinin [bird-offerings (from "kan tzippor," a bird's nest). There are weighty halachoth pertaining to them, such as a mandatory offering being mixed up with a gift-offering; or a burnt-offering, whose services are "above," being mixed up with a sin-offering, whose services are "below"], and pithchei niddah [the halachoth of a niddah who has lost track of her menstrual time and must be vigilant to determine its onset (Sometimes she must immerse herself ninety-five times, according to the view that immersion in its prescribed time is a mitzvah)] — [kinin and pithchei niddah] are the foundation of halachoth (the oral law), [for which reward is received.] Tekufoth [the movements of the constellations] and gematrioth [the numeration of the letters] are the "seasonings" of wisdom, [like those which it is customary to eat at the end of a meal for dessert. So, these wisdoms honor their possessors in the eyes of men.]
Avot D'Rabbi Natan
Rabbi Meir would say: Beloved is the human being, who was created in the image of God, as it says (Genesis 9:6), “For in God’s image did God make the human.” Beloved are Israel, who are called children of the Omnipresent God, as it says (Deuteronomy 14:1), “You are children of the Eternal your God.” Beloved are Israel, for they were given a valuable tool. With it the world was created, as it says (Proverbs 4:2), “For I have given you a good thing; do not forsake My Torah.”)
Rabbi Eliezer bar Tzadok would say: What are the righteous like in this world? Like a tree that is planted in a pure place, but its branches extend out to an impure place. What do people say? Cut off that tree’s branches so that all of it will be pure, as it should be. What are the wicked like in this world? Like a tree that is planted in an impure place, but its branches extend out to a pure place. What do people say? Cut off that tree’s branches so that all of it will be impure, as it should be.