Persevering in faith always means a struggle for believers at all times and in all circumstances. The opposition can be very different. In Philippi there are fierce opponents. It is not stated exactly who they are. Based on Philippians 3:2 some think of Jewish false teachers. It is more likely that these are opponents from the pagan environment in Philippi. There, for example, the Roman emperor was venerated. Most citizens and perhaps also relatives took part in it. We should think here of the beginnings of persecution: harassment, contempt, slander, threats of violence, and perhaps violent action.
Paul exhorts the Philippians not to be intimidated by their opponents in any way. He gives far-reaching encouragement. If the Christians remain steadfast in the faith, it is a sign, an indication, in two ways. It is a sign to their adversaries that they are heading for their downfall. And a sign to the believers that they are being saved. Paul adds: this sign comes from God.
Seen in this way, persecution and oppression have great significance. When the believers stand firm, the supremacy of Christ the Lord becomes apparent in a world that reveres the emperor as lord—also in any other situation of oppression, and with a view to the great day of Christ when he will judge all the powers that oppose him. In 2 Thessalonians 1:4–10 Paul writes about this in more detail.
28 and not frightened in anything by your opponents. This is a clear sign to them of their destruction, but of your salvation, and that from God.