Here also, from the verse,“how he met thee (karcha) by the way,”  we learn that Amalek set against thee that evil serpent on high in order to defile you on all sides. And if Moshe had not waged a mighty spiritual battle on high, and Yehoshua a mighty war down below, Israel would not have been able to overcome him. It is for this reason that the Holy One Blessed Be He insisted on preserving the memory of this hatred from generation to generation. What is the reason? Because Amalek strove to uproot the sign of the Brit (Israel’s sexual purity) from its place.

Zohar, Vayikra 49b
Rabbi Abba said, I see that the masses pay no attention to, and are ignorant of, the honor due to their Master.

It is written of Israel, “I have set you apart from the nations to be mine,” (Vayikra, 20:24) and it is written, “You shall sanctify yourselves and be holy, for I, the L-rd, am holy,” (Ibid, 11:44.)

If they distance themselves from G-d (by following after their lusts,) where is their holiness, since their desires turn them away from Him? About this, the verse proclaims, “Be not as the horse, nor as the mule which have no understanding,” (Tehillim, 32:9.) How are men distinguished from the horse and the mule? By sanctifying themselves, and by perfecting themselves, and by distinguishing themselves from all other beings.

Therefore, a man’s marital relations should be at established times, in order that he may concentrate his desire on cleaving to the Holy One Blessed Be He. Behold, we have emphasized that at midnight, G-d enters the Garden of Eden to take pleasure in the tzaddikim, and then Knesset Yisrael (the Shechinah) praises Him. This is the favorable time to cleave to Him.

At this time, the disciples who study the Torah (at midnight) join Knesset Yisrael in praising the Holy King by their study of Torah.

All other men at this favorable time should sanctify themselves in
G-d (during their marital relations) and concentrate their desires on cleaving to the Holy One Blessed Be He.

For the Torah scholars, their marital union should be at the time when there is another (supernal) union, and this is from one Sabbath (midnight) to the next Sabbath (midnight,) in order to concentrate their desire on cleaving to the Holy One Blessed Be He and Knesset Yisrael. For this is a favorable time Above when all of the worlds, the upper and the lower, are blessed.

If men distance themselves from Him and behave like beasts during their marital relations, where is their holiness in their duty to be holy? Where are those holy souls that could have been brought down from Above? Regarding this, King Shlomo cried out and proclaimed, “Also the soul without knowledge is not good,” (Mishle, 19:2.) What knowledge does this refer to? The knowledge of the Holy One Blessed Be He (during marital relations.) When this occurs, then the soul is not good. This is the soul that is drawn down to their offspring through their marital relations, it is not good, for this soul is drawn down from the Sitra Achra (the realm of evil called the “Other Side”) and this is not a good soul, for their hearts are not concentrated on G-d.  

A man who incites himself with the evil inclination, and who does not focus his intention and the desire of his heart on G-d, the soul which he draws down comes from the side of the evil inclination, and this soul is not good. This is the meaning of, “Also the soul without knowledge is not good.”

Whoever races forward transgresses. Someone who hurries (to have relations) and ignores the favorable time, without desiring to sanctify the act, he behaves sinfully. He acts wrongly in every aspect.
 
And this is the reason that evil diseases fall upon men, and bear witness against them because of their brazenness, and reveal that G-d is repelled by them, and that He will not look on them with favor until they repent and mend their ways and return to their original purity.

Zohar, Vayikra 81b
And when is a man called “one?” When the man and his wife are together, and he sanctifies himself with an exalted holiness, and his intention is directed toward sanctification (during their marital relations.)  Behold, when a man is engaged in marital relations, and he strives to sanctify the act in the proper fashion, then he is whole and is called “one” without blemish. For this reason, a man should make his wife happy at this time, in order that they should share the same desire and the same intention. And when they are united in this manner, then they are completely one; one soul and one body. Their soul is one through their shared desire to cleave one to the other. And their body is one, for as we have learned, a man who is not married is in a state of separation, and only when male and female are united do they form one body. Thus, they are one soul and one body, and are called one person. Then the Holy One Blessed Be He rests upon that oneness, and infuses it (the offspring of that holy union) with a spirit of holiness. These (offspring) are the ones referred to as, “sons of HaKodesh Baruch Hu,” as has been said, and thus it is written, “Be holy for I, Hashem, am holy.”

Zohar, Vayikra 84a
We have learned, it is forbidden for a man to gaze upon the beauty of a woman, so that he should not come to have evil thoughts and thus be incited to something worse (the wasting of semen. See Avodah Zara, 20b.)

For this reason, when Rabbi Shimon had to walk through the town, followed by his disciples, whenever he came to a place that beautiful women were apt to be found, he would to lower his eyes and say to his companions, “Do not turn aside!” (“after foreign gods.”)

For whoever gazes at the beauty of a woman by day, will have sinful thoughts at night. And if these evil thoughts overcome him, he transgresses the commandment, “Thou shall not make for yourselves molten gods.”  Furthermore, if he has marital relations with his wife while thinking about these evil images, the children born from such union are called “molten gods.” For this reason, it is written, “Do not turn astray after their gods,” and, “Thou shall not make for yourselves molten gods.”

Zohar, Devarim 266a
As they walked along, Rabbi Abba said, What is the meaning of the verse: “They have forsaken Me, the fountain of living waters, and have hewn them out cisterns, broken cisterns that can hold no water?” (Yirmeyahu, 2:13)

The meaning of  “they have forsaken Me (oti)” refers to one who has forsaken “my sign,” by being false to the imprint of the holy Brit. And how does he betray it? By bringing it into a foreign domain, as is said, “and took for himself the daughter of a foreign god,”  (Malachi, 2:11.) These women are called “broken cisterns,” for all of the gentile nations are broken cisterns.

But Israel's women are “a well of living waters.” This is a holy domain, of a holy faith, and it is called a flowing well of pure, streaming waters, as is said, “streams from Lebanon,” (Shir HaShirim, 4:15) and, “Drink waters out of your own cistern, and running waters out of your own well,” (Mishle, 5:15.) Also, it is written, “A fountain of gardens, a well of living waters,” (Shir HaShirim, 4:15) But the other domain (Sitra Achra) is called, “broken cisterns than can hold no water.”

Behold, the ever-flowing stream above (Yesod) waters all the Garden (Malchut) and irrigates every place, as we have already explained, until it fills that place in the Garden which is called “the well of living waters,” which nourishes all of the upper and lower worlds, as is said, “And from there it was parted,” (Bereshit, 2:10.)

But all the sides of the Left Side are not watered from that fountain of flowing water, because they are of the side of the other nations, and they are called “broken cisterns.”

And one who is false to the holy imprint of the Brit cleaves to this side of the broken cisterns that do not hold water, because the water does not flow into them.

While the man who merits to guard the Brit properly merits to drink of the waters of that flowing stream in the world to come, and causes that upper well to be filled in order to send forth blessings above and below. Fortunate is he in this world and in the world to come. About him it is written, “And thou shall be like a watered garden, and like a spring of water whose waters never fail,” (Yishayahu, 58:11.)