The sexual act unites body, soul, and spirit: that is the basis of marriage. Marriage is not established by forms, words, or laws, but by sex. When the sexual act is performed, the partners are married chemically.
"Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh." —Genesis 2:24
"Wherefore they are no more twain, but one flesh." —Matthew 9:6
The verse, "And Isaac brought her into his mother Sarah's tent" (Genesis 24.67), our masters have interpreted to mean that the Divine Presence came into Isaac's house along with Rebecca. According to the secret doctrine, the supernal Mother is together with the male only when the house is in readiness and at the time the male and female are conjoined. At such time blessings are showered forth by the supernal Mother upon them." —Zohar
"Bachelors and bachelorettes must find a spouse if they want to Christify themselves, because the Gnostic esotericists can only perform sexual contact when they are married. The fires cannot be awakened without sexual magic: yes, without chastity, nothing is achieved in these studies. Kill desire, kill the “I,” and its thoughts: this is how you will become a liberated one. Remember, true marriage has nothing to do with the social or religious formulas of this barbaric humanity. The authentic marriage is performed when a couple unites in spirit, soul, and sex; the true marriage must be pure like a lotus flower." - Samael Aun Weor, The Major Mysteries