True friendship, especially between Christians, can have a fragile side. On the one hand, one of the reasons for friendship is personal, the need to have someone close with whom to share joys, sorrows and everyday events. On the other hand, the goal of all truly Christian friendship is growth in Christ on the part of both parties. And that's the fragile part: how to be gently honest with a friend without jeopardizing the relationship. That's where Paul now is in his relationship with the Philippians. He intends to send Timothy to find out whether this letter will have done any good; but he wants to do so without implying that he is really just checking up on them.
Verse 19 sets out the basic datum and its reason—a proposed visit by Timothy, with the hope of cheering Paul by (further) news about "your affairs" (NIV about you; see commentary on 1:27), presumably whether his letter has had any effect. Since this needs explanation, verses 20-22 offer a twofold justification for the sending of Timothy, which turns out to be only partly justification for doing so at all, and mostly justification for sending Timothy in particular. But the explanation gets away from Paul a bit, so in verses 23-24 he returns to the basic datum—the sending of Timothy—but with two additional pieces of information: Timothy is to be sent as soon as Paul has some sense about "his own affairs" (NIV how things go with me); and he himself will come as soon as possible. These pick up items from 1:19-20 and 24-26.
But it is not possible even here for the apostle to speak without expressing concern for the gospel. So along with the basic issue of his and their relationship, and his concern about them, the explanatory "commendation" of Timothy (vv. 20-22) has the gospel as its underlying current, becoming explicit at the end of verse 22.
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