Paul’s instruction regarding the betrothed should not be taken as a moral command. It is meant as loving counsel, by which he wishes to spare God’s people from worldly troubles.
The phrase worldly troubles
is a good translation of a phrase that literally means tribulation in the flesh.
Especially in times of persecution (see 1 Corinthians 7:26), a married person will experience added troubles, due to concern for a spouse and children.
28 But if you do marry, you have not sinned, and if a betrothed woman marries, she has not sinned. Yet those who marry will have worldly troubles, and I would spare you that.