Charles Ellicott Commentary 1 Corinthians 1:9

"God is faithful, through whom ye were called into the fellowship of his Son Jesus Christ our Lord." — 1 Corinthians 1:9 (ASV)

God is faithful.—The One who called them “unto the communion of His Son” is faithful, and therefore He will complete His work; no trials and sufferings need make them doubt that all will at last be well. The same confidence is expressed in Philippians 1:6, and 1 Thessalonians 5:24.