The Catechism of the Catholic Church has
1604 God who created man out of love also calls him to love the fundamental and innate vocation of every human being. For man is created in the image and likeness of God who is himself love.90 Since God created him man and woman, their mutual love becomes an image of the absolute and unfailing love with which God loves man. It is good, very good, in the Creator's eyes, and this love which God blesses is intended to be fruitful and to be realized in the common work of watching over creation: "and God blessed them, and God said to them: 'Be fruitful and multiply, and fill the earth and subdue it.'"91
90 Cf. ⇒ Gen 1:27; ⇒ 1 Jn 4:8, ⇒ 16.
91 ⇒ Gen 1:28; cf. ⇒ 1:31.
The primary reference for this question is Genesis 1:28 with other references, enumerated below.
The Catechism further extols the virtue of marriage with
1613 On the threshold of his public life Jesus performs his first sign — at his mother's request — during a wedding feast.105 The Church attaches great importance to Jesus' presence at the wedding at Cana. She sees in it the confirmation of the goodness of marriage and the proclamation that thenceforth marriage will be an efficacious sign of Christ's presence.
1616 This is what the Apostle Paul makes clear when he says: "Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her," adding at once: "'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one. This is a great mystery, and I mean in reference to Christ and the Church."110
105 Cf. ⇒ Jn 2:1-11.
110 ⇒ Eph 5:25-26, ⇒ 31-32; Cf. ⇒ Gen 2:24.
Thus marriage is seen as a metaphor for the relationship between Christ and the Church:
It is God's purpose that, as husband and wife give themselves to each other in love throughout their lives, they shall be united in that love as Christ is united with his Church. [Church of England, also CCC1617]
Thus there are two purposes to marriage: to procreate, and to model the relationship between Christ and the Church. Paul's reference to burning with passion might be seen as a desire to become one flesh: to make present that relationship (even if that second purpose might not be exactly uppermost in their mind!) In that case, marry, and demonstrate it.
Gen 1:27 — So God created man in his own image, in the image of God he created him; male and female he created them.
Gen 1:28 — And God blessed them, and God said to them, "Be fruitful and multiply, and fill the earth and subdue it ..."
Gen 1:31 — And God saw everything that he had made, and behold, it was very good.
Gen 2:24 — Therefore a man leaves his father and his mother and cleaves to his wife, and they become one flesh.
Jn 2:1–11 — Wedding at Cana in Galilee
Eph 5:25–26 — Husbands, love your wives, as Christ loved the church and gave himself up for her, that he might sanctify her, having cleansed her by the washing of water with the word.
Eph 5:31–32 — "For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh." This mystery is a profound one, and I am saying that it refers to Christ and the church.
1 Jn 4:8 — He who does not love does not know God; for God is love.
1 Jn 4:16 — ...God is love, and he who abides in love abides in God, and God abides in him.