Again.. in heaviness] a clear reference to a visit to Corinth, which gave him much pain, subsequent to his writing the First Epistle (see Intro.).
By the will of God] He asserts his divine call to office in presence of opposition: cp. 1 Corinthians 1:1; Galatians 1:1, and contrast Philippians 1:1; 1 Thessalonians 1:1, in cases where his relations to the Church were happy. Saints] A common designation of the Christian converts. It reminded them of the life to which they were consecrated at baptism. Achaia] probably used in a loose popular sense for the country around Corinth: cp. 1 Corinthians 1:2.