Gaius mine host - Who has received me into his house, and shown me hospitality. The word “host” means one who entertains another at his own house without reward.
And of the whole church - Who has opened his house to entertain “all” Christians; or to show hospitality to them all. He was baptized by Paul himself at Corinth 1 Corinthians 1:14; and was so highly esteemed by the church that John wrote an epistle to him; 3 John 1:1. He was probably a wealthy citizen of Corinth, who freely opened his house to entertain Christians, and for the purpose of religious worship.
Erastus - Erastus is mentioned Acts 19:22 as having been sent by Paul with Timothy into Macedonia. He is also mentioned 2 Timothy 4:20 as having resided at Corinth.
The chamberlain - A chamberlain is properly an officer who has charge of a chamber, or of chambers. In England, the lord chamberlain is the sixth officer of the crown, and has charge of the king’s lodgings, and wardrobe, etc. He has also an important rank on days of public solemnities, as the coronation day, etc. The word used here is commonly in the New Testament translated “steward.” It properly means one who has charge of domestic affairs, to provide for a family, to pay the servants, etc. In this place it means one who presided over the pecuniary affairs of the “city,” and should have been translated “the treasurer; the city treasurer;” an once of trust and of some importance, showing that, “all” who were converted at Corinth were not of the lowest rank. This is implied in 1 Corinthians 1:26, “Not many wise men, not many mighty, not many noble, are called,” implying that there were some such.
Quartus a brother - A fellow-Christian.