1 Timothy 5:9-15
9 Let not a widow be taken into the number under threescore years old, having been the wife of one man,
10 Well reported of for good works; if she have brought up children, if she have lodged strangers, if she have washed the saints' feet, if she have relieved the afflicted, if she have diligently followed every good work.
11 But the younger widows refuse: for when they have begun to wax wanton against Christ, they will marry;
12 Having damnation, because they have cast off their first faith.
13 And withal they learn to be idle, wandering about from house to house; and not only idle, but tattlers also and busybodies, speaking things which they ought not.
14 I will therefore that the younger women marry, bear children, guide the house, give none occasion to the adversary to speak reproachfully.
15 For some are already turned aside after Satan.
The Grace New Testament Commentary - 1 Timothy 5:11-15
5:11-15 Verse 11 indicates that other widows, presumably those younger than 60, were not to be put on the list. Why? Because evidently to be on this list the women had to use their energies in serving in the church. In other words, these unmarried women would do what they could to help in the church.
However, putting younger women on the list might cause them to cast off their first faith when they desire to marry. Most likely Paul is thinking of a woman who would so desire to marry that she'd marry an unbeliever, one outside the faith. After all, there were few believing men to choose from. Paul was not concerned that a younger woman on the list might marry a Christian (cf. v 14). But by marrying an unbeliever, she would become part of the faith of her husband, a different faith. That would be an affront to the church which had been supporting her.
Another danger is that younger women supported by the church might learn to be idle…and not only idle but also gossips and busybodies. They could easily develop bad and destructive habits. Thus Paul desires that the younger widows marry, bear children, and manage the house. Implied, of course, is that they only marry "in the Lord" (cf. v 12: 1 Cor 7:39). When a woman is involved in raising a family and managing a house, she gives no opportunity to the adversary to speak reproachfully. The adversary here is Satan as Paul makes clear in v 15, though it could include humans who like Satan oppose the church.
Evidently some young widows had already turned aside after Satan, which in this context refers to marrying unbelievers and departing from the Christian faith. Whereas today most women are led to believe that true fulfillment comes from having careers outside the home, the Scriptures teach that true fulfillment for women comes from raising godly children and managing their homes.