Stephanas was one of the early Christians of Achaia (the city of Corinth was in Achaia - see the Fact Finder question below). His family were among the first, and few, who were personally baptized by the apostle Paul (see Paul's Ministry). Some have assumed that Stephanas may have formerly been the jailer who released Paul after a miraculous earthquake and was baptized with his family. While possible, there is no way to be certain of that, since the jailer is not named (i.e. Acts 16:23-34). He was however a loyal and devout Christian after his conversion.
As stated in the verses below, Stephanas was one of the few people who were personally baptized by the apostle Paul, not because Paul didn't regard Baptism (see also The Origin of Baptism) as very important (Paul himself was baptized upon conversion) but rather that there were many others who tended to it i.e. "first apostles, secondarily prophets, thirdly teachers, after that miracles, then gifts of healings, helps, governments, diversities of tongues" (1 Corinthians 12:28 KJV). Paul himself was baptized by a "lay member," Ananias (Acts 9:10-19). These verses also reveal how the Church sometimes had, and has, personality clashes among strong-willed people (Paul and Peter apparently stayed well clear of each other most of the time).
"For it hath been declared unto me of you, my brethren, by them which are of the house of Chloe, that there are contentions among you. Now this I say, that every one of you saith, I am of Paul; and I of Apollos; and I of Cephas [i.e. Peter]; and I of Christ."
"Is Christ divided? was Paul crucified for you? or were ye baptized in the name of Paul? I thank God that I baptized none of you, but Crispus and Gaius; Lest any should say that I had baptized in mine own name. And I baptized also the household of Stephanas: besides, I know not whether I baptized any other. For Christ sent me not to baptize, but to preach the Gospel: not with wisdom of words, lest the cross of Christ should be made of none effect. For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God." (1 Corinthians 1:11-18 KJV)
Stephanas' household is referred to here as "the firstfruits of Achaia," meaning that they were among the first Christians in that region. The King James use of the word "addicted" in "they have addicted themselves to the ministry of the saints" is used to translate the original Greek word (pronounced) tas-so which means assigned; they assigned, or dedicated, themselves to the service of the church, as plainly described by Paul:
"But I will tarry at Ephesus until Pentecost. For a great door and effectual is opened unto me, and there are many adversaries."
"Now if Timotheus [i.e. Timothy] come, see that he may be with you without fear: for he worketh the work of the Lord, as I also do. Let no man therefore despise him: but conduct him forth in peace, that he may come unto me: for I look for him with the brethren."
"As touching our brother Apollos, I greatly desired him to come unto you with the brethren: but his will was not at all to come at this time; but he will come when he shall have convenient time."
"Watch ye, stand fast in the faith, quit you like men, be strong. Let all your things be done with charity."
"I beseech you, brethren, ye know the house of Stephanas, that it is the firstfruits of Achaia, and that they have addicted themselves to the ministry of the saints, That ye submit yourselves unto such, and to every one that helpeth with us, and laboureth [see also Labourers Of The Harvest]. I am glad of the coming of Stephanas and Fortunatus and Achaicus: for that which was lacking on your part they have supplied. For they have refreshed my spirit and yours: therefore acknowledge ye them that are such." (1 Corinthians 16:8-18 KJV)
Fact Finder: Where was Achaia?
See Paul In Achaia