What does 1 Cor 7:9 mean, “it is better to marry than to burn.”

The meaning of the passage is fairly straightforward. The apostle is giving advice to the single, whom he refers to as the unmarried and the widows. It is, he states, good or advisable for them to remain in their single state for the reasons spelled out in 7:26, 32-35. (Observe that in another situation Paul counsels the younger widows to marry [1Tim 5:14].) But now he hastens to add a postscript. If the situation is such that these persons cannot control their sexual desires, they should marry. The explanation Paul gives is that it is better to get married than be inflamed with sexual desire, which is hard to control outside of marriage. The verb “pyrousthai,” is related to “pyr” (“fire”), means “burn” or “be enflamed,” and is here used figuratively of sexual desire. (cf. Expositor’s Bible Commentary, 1 Corinthians)