The church that is in their house - Aquila and Priscilla are mentioned Acts 18:26 as having received “Apollos” into their family, to instruct him more perfectly. The church in their house is also mentioned 1 Corinthians 16:19. This may mean either the church that was accustomed to assemble for worship at their hospitable mansion; or it may mean their own family with their guests, regarded as a “church.” In those times Christians had no houses erected for public worship, and were therefore compelled to meet in their private dwellings.
Salute - The same word before translated “greet.”
Who is the first-fruits - One who first embraced Christianity under my preaching in Achaia. The “first-fruits” were a small part of the harvest, which was first gathered and offered to the Lord; Exodus 22:29; Exodus 23:16; Leviticus 2:12; Deuteronomy 18:4. In allusion to this, Paul calls Epenetus the first-fruits of the great spiritual harvest which had been gathered in Achaia.
Achaia - See the note at Romans 15:26. This name and those which follow are chiefly “Greek,” but we know little of the persons mentioned, except what is here recorded.