1. a man will leave his father and mother. The marriage relationship comes before all others including our relationship with our parents. When a couple marry they set up a new family unit.
2. and be united to his wife. Marriage is the union of one man and one woman in intimate, life-long relationship and companionship.
3. and the two shall become one flesh. This refers to sexual intimacy which comes after leaving and being united and so is kept for marriage.
In our short life on earth, it is possible to bring God glory either in marriage or as a single adult. Neither is a higher or more spiritual calling because for both men and women our first marriage is to Christ. We are His bride.
The wedding of the Lamb has come. The Bible closes with the wedding of Christ and the church. Every human marriage points forward to that glorious day and every Christian, married or single, is fully part of it for ever.