Adam Clarke on 1 Corinthians 1:10

Now, if Timotheus come - Of Timothy we have heard before, 1Cor 4:17. And we learn, from Act 19:22, that Paul sent him with Erastus from Ephesus to Macedonia. It is evident, therefore, in opposition to the very exceptionable subscription at the end of this epistle, that the epistle itself was not sent by Timothy, as there stated.

That he may be with you without fear - That he may be treated well, and not perplexed and harassed with your divisions and jealousies; for he worketh the work of the Lord - he is Divinely appointed, as I also am.