The following is an excerpt from
The MacArthur New Testament Commentary on 2 Timothy 1.
For I am mindful of the sincere faith within you, which first dwelt in your grandmother Lois, and your mother Eunice, and I am sure that it is in you as well. (2 Timothy 1:5)
Timothy had a heritage of sincere faith within [him], which first dwelt in [his] grandmother Lois, and [his] mother Eunice. The reference to Lois and Eunice suggests that Paul knew those women personally and perhaps was instrumental, along with Barnabas, in winning them to Christ during his first missionary journey, which had taken him through Timothy’s home area of Galatia (See Acts 13:13–14:21). They probably were Jewish believers under the Old Covenant who immediately received Jesus as their Messiah, Savior, and Lord when they first heard the gospel from the lips of Paul. By the time of Paul’s second journey, the women had led their grandson and son to the Lord, and he already had become “well spoken of by the brethren who were in Lystra and Iconium” (Acts 16:2). Timothy was Paul’s indirect son in the faith who had come to belief through the witness of his grandmother Lois and his mother Eunice, who had been led to faith directly by the apostle. Through them, he had “from childhood… known the sacred writings which are able to give [him] the wisdom that leads to salvation through faith which is in Christ Jesus” (2 Tim. 3:15).
Some years ago I was involved in a discussion regarding the choice of a man to take up the leadership of a well-known Christian organization. In looking over the list of prospects, I commented that it was interesting that every one of those men had a godly pastor for a father. The Lord has, of course, raised up many faithful leaders, including Paul, from ungodly and even godless families. But a high percentage of the great men throughout church history have come from godly homes. Timothy’s father was an unbelieving Gentile (Acts 16:3), but his mother and grandmother were believers of great godliness. Paul commends them for the immense influence for good they had on Timothy and for the sincere faith that the apostle was sure to be in Timothy as well.