Of what was God a witness?

Of the love of Christ in Paul that was directed toward the saints in Philippi. v8

“Only someone who has been poured out in love for other people can understand what Paul was saying in verse eight. Most Christians have many opportunities throughout their lifetimes to bear witness of Jesus Christ. It appears that to some Christians there is given a missionary love for a specific race, nation, or group of people. It is the love of Jesus Christ that is being expressed toward the particular group of people.”