Tzava'at Harivash 5-6

I.e., the focus of your thought should always be on the supernal spirituality, as opposed to the mundane. Thus you yourself, too, will be attached to spirituality (see below, sect. 69). Cf. below, sect. 8 and 24.

See Maimonides, Hilchot De'ot 3:2 and ch. 4.

Man is affected by what he sees, positively or negatively. To view something good or holy has positive effects. For example, to gaze at the tzitzit (ritual fringes on certain garments, ordained in Numbers 15:38ff.) will lead to observance of mitzvot, as it is written “you will see it and remember all the commandments of God and do them” (ibid. verse 39). In turn, to gaze at the physical and mundane will arouse desires related to it and, therefore, lead to wrongful actions in their pursuit: “The eyes see and the heart covets, and the body commits the sin.” (Commentary of Rashi on Numbers 15:39) See also below, sect. 121, and cf. sect. 50 and 90.

The phrase is from Tikunei Zohar 21:48b. The physical body seeks physical pleasure that defiles and leads astray, even as the original serpent enticed Adam and Eve. This does not mean, however, that the body is evil per se. It is the outer garment to the soul, allowing the soul to function in this world with the performance of mitzvot. Thus it is not equivalent to the serpent but only to the “skin of the serpent,” i.e., its external aspect. As such it is an admixture of good and evil, allowing man’s freedom of choice to do good or evil (see ibid. 67:98a)