One does not Know the Taste of Sweet until He Tastes Bitter
“It is written of the Tree of Knowledge of Good and Evil: And YHWH showed him a tree, and he flung it into the water, and the water turned sweet (Exodus 15:25). Since the children of Israel were with the mixed multitude, they were of the Tree of Knowledge of Good and Evil. Therefore, it is half sweet from the right and half bitter from the left. When the mixed multitude caused the children of Israel to sin, it was as if all were on the Other Side. Consequently, the waters returned to their bitter state like the tree in the water. This is what is meant by and they came to Marah, and could not drink water from Marah, for it was bitter (Exodus 15:23). The bitter tree was similar to the test of a סוֹטָה (sotah), suspected wife. If she indeed strayed from her husband, the waters which she was made to drink turned bitter, and because of them her belly will swell, and her thigh sag (Numbers 5:27). If she did not stray, it is written she will be cleared, and sown with seed (ibid., 28), and give birth to a son. Here too, the waters were made sweet.
… The Tree of the Knowledge of Good and Evil, forbidden and permitted, pure and impure, will no longer apply to the children of Israel, since our sustenance will be solely from the side of the Tree of Life, where there are no contradictions stemming from the Other Side, nor any strife nor difference stemming from the unclean spirit, as is written And also I will cause… the unclean spirit to pass out of the land (Zechariah 13:2)” (Zohar 3:125a, Ra’aya Meheimna Naso).
“It has been taught: It is incumbent upon a person who studies wisdom to study some foolishness and now it, because thereby wisdom derives benefit—just as light derives some benefit from darkness, for were it not for darkness, light would not be recognized and the world would gain no benefit from it… This may be compared to sweet with bitter, for a person does not know the taste of sweet until he tastes bitter. What makes this sweet? You must admit, bitter. This corresponds to what is written: One against the other God has set (Ecclesiastes 7:14)” (Zohar 3:47b, cf. Ecclesiastes 2:13).