And Tychicus - See Acts 20:4. In Ephesians 6:21, Paul calls him "a beloved brother, and faithful minister in the Lord." But it may be asked why he did not retain him with him, or why should he have sent him away, and then call Timothy to him? The probability is, that he had sent him before he had seen reason to apprehend that he would be put to death; and now, feeling the need of a friend to be with him, he sent to Timothy, rather than to him, because Tychicus had been employed to perform some service which he could not well leave, and because Paul wished to give some some special instructions to Timothy before he died.
Have I sent to Ephesus - Why, is not certainly known; compare Intro. Section 2.

Tychicus have I sent to Ephesus - For this person, see Acts 20:4; Ephesians 6:21; Colossians 4:7. It is rather strange that the apostle should say, I have sent Tychicus to Ephesus, if Timothy was at Ephesus at this time; but it is probable that Tychicus had been sent to Ephesus some time before this, and therefore the apostle might say, though writing now to Ephesus, Tychicus have I sent, etc.

And Tychicus have I sent to Ephesus. To supply the place of Timothy, while he came to Rome, and continued there: so careful was the apostle of the church there, that they might not be without the ministry of the word during his absence; see Ephesians 6:20.

And--Greek, "But." Thou art to come to me, but Tychicus I have sent to Ephesus to supply thy place (if thou so willest it) in presiding over the Church there in thy absence (compare Titus 3:12). It is possible Tychicus was the bearer of this Epistle, though the omission of "to thee" is rather against this view.