"When Timothy comes, see to it that he has nothing to fear while he is with you, for he is carrying on the work of the Lord, just as I am. No one, then should treat him with contempt. Send him on his way in peace so that he may return to me. I am expecting him along with the brothers." NIV translation
Now, Paul commends Timothy to the Corinthians. He was in Ephesus with Paul but was being sent on to Macedonia and Corinth. He reminds the Corinthian believers that, regardless of his age, Timothy was a servant of Jesus Christ and should be treated with the same respect that they would show to Paul.
"Now about our brother Apollos: I strongly urged him to go to you with the brothers. He was quite unwilling to go now, but he will go when he has the opportunity." NIV translation
Apollos had evidently left Corinth due to the controversy about following him versus following Paul. Paul had urged him to return with this letter settling the matter. Paul made this point so that they would not think that he had kept Apollos from returning. Once again, this reminds us that there is no place for jealousy in the work of Christ. In Christ, we are all working for His glory and not our own.
"Be on your guard; stand firm in the faith; be courageous; be strong. Do everything in love." NIV translation
Paul reminds the believers to put into practice what he has said in this letter. It reminds us that we are to be doers of the word and not just hearers. God's word has the power to change us but we have to make the choice to take it in.
"You know that the household of Stephanas were the first converts in Achaia, and they have devoted themselves to the service of the Lord's people. I urge you, brothers and sisters, to submit to such people and to everyone who joins in the work and labors at it." NIV translation
These were Greek converts and Paul had baptized them. They had put their faith into action and Paul urged the Corinthian church to do the same. The "submit" is talking about responding to them with love as they serve the Lord.
"I was glad when Stephanas, Fortunatus and Achaicus arrived, because they have supplied what was lacking from you. For they refreshed my spirit and yours also. Such men deserve recognition." NIV translation
These were probably the men that brought Paul the letter from the believers in Corinth. As we can tell, Paul was glad for any fellowship with believers in Corinth. As Christians, we are all called to build each other up in the faith. Sometimes that is done simply by getting together and feeling the sense of unity in the faith.