And having this confidence - “Being persuaded of this, that my continuance on earth is desirable for your welfare, and that the Lord has a work for me to do, I confidently expect that I shall be permitted to live.” The “confidence” here referred to was, that his life was needful for them, and hence that God would spare him. A literal translation would be, “And being persuaded as to this, or of this” - τοῦτο πεποιθὼς touto pepoithōs - “I know,” etc. The foundation of his expectation that he should live does not appear to have been any revelation to that effect, as Doddridge supposes; or any intimation which he had from the palace of the intentions of the government, as some others suppose, but the fact that he believed his life to be necessary for them, and that therefore God would preserve it.
I know that I shall abide - The word “know,” however, (οιδα oida) is not to be pressed as denoting absolute necessity - for it appears from Philippians 1:27 and Philippians 2:17, that there was some ground for doubt whether he would live - but is to be taken in a popular sense, as denoting good courage, and an earnest hope that he would be permitted to live and visit them. Heinrichs.
And continue with you all - That is, that he would be permitted not only to live, but to enjoy their society.
For your furtherance and joy of faith - For the increase of your faith, and the promotion of that joy which is the consequence of faith. Wetstein has quoted a beautiful passage from Seneca (Epis. 104) which strikingly resembles this sentiment of Paul. He says that when a man had meditated death, and when on his own account he would be willing to die, yet that he ought to be willing to live - to come back again to life - for the sake of his friends. Pagan adds: “It pertains to a great mind to be willing to come back to life for the sake of others; which distinguished people often do.”