Jamieson, Fausset and Brown on 1 Corinthians 1:11

11. (1Co 11:18).

by them ... of ... house of Chloe--They seem to have been alike in the confidence of Paul and of the Corinthians. The Corinthians "wrote" to the apostle (1Co 7:1), consulting him concerning certain points; marriage, the eating of things offered to idols, the decorum to be observed by women in religious assemblies. But they said not a syllable about the enormities and disorders that had crept in among them. That information reached Paul by other quarters. Hence his language about those evils is, "It hath been declared unto me," &c.; "It is reported commonly" (1Co 5:1, 2). All this he says before he refers to their letter, which shows that the latter did not give him any intimation of those evils. An undesigned proof of genuineness [Paley, Horæ Paulinæ]. Observe his prudence: He names the family, to let it be seen that he made his allegation not without authority: he does not name the individuals, not to excite odium against them. He tacitly implies that the information ought rather to have come to him directly from their presbyters, as they had consulted him about matters of less moment.

contentions--not so severe a word as "divisions," literally, "schisms" (1Co 1:10, Margin).