Paul states in 1:24-26 that he anticipates his release and that he will come to minister again in Philippi. But given some uncertainty as to when he will arrive, he focuses their attention on one purpose: "Only [this is the singular focus] conduct yourselves in a manner worthy of the gospel of Christ" (1:27a). He calls them to live worthy of the gospel. Now, the Philippians weren't newbies in the Christian faith. They engaged in the defense and confirmation of the gospel (1:7). They supported the gospel ministry (1:5). And they had done this for 10+ years! Do they really need such an elementary instruction? They did, because they lacked a crucial area of this worthy conduct: unity.
Unity (27c): Paul develops this aspect of the gospel-worthy conduct at the end of 1:27: "so that … you are standing firm in one spirit, with one mind striving together for the faith of the gospel" (1:27c). The emphasis on unity is clear enough! And this unity is expected of those living worthy of the gospel. It is not enough that one stands firm in the gospel by himself. We are to stand firm together! Even the next verbal phrase "strive together" points out this unity. This phrase depicts a team working toward a single goal. And the goal Paul has in mind is for the church to counter the secular and unbiblical world-view and defend the Christian faith. Now, lest we think this is a doctrinal battle only, we must not forget the very first imperative which dealt with our conduct. We not only strive together for the faith, but we also obey the gospel's call to discipleship, and we do this together in unity with one another.
Confidence (28a): Now, the Philippians had "opponents" (1:28), i.e., persecutors. And their oneness as a church was to embolden them against these adversaries. They were to link arms with one another and not be intimidated. When we are facing enemies outside the church, unity inside is an absolute must! If envy, divisions and strife are brewing internally, we will hardly withstand the onslaught of the unbelieving world around us.
Sign (28b-30): Christian courage is "a sign of destruction" for the enemies. When persecutors see believers bravely suffer for Christ, they witness God's testimony of their own indictment—they are guilty of injustice and hatred toward God's righteous people (cf. Matt. 27:4). Finally, Paul assures them that their suffering is much like his own, and that persecution is not a curse to shun but a gift to welcome. This only proves that we truly belong to Christ.
 This gospel-worthy conduct should be evident "whether I come and see you or remain absent" (1:27b).
 "Worthy of the gospel" can be analogous to a conduct worthy of one's family name. One may bring shame upon his own family by a scandalous lifestyle. Actions unworthy of his family will bring shame to his family.
 Philippi was evangelized ~50 AD and this letter was written ~60-62 AD.
 "so that" in verse 27 shows "standing firm in one spirit, with one mind" comes from gospel-worthy conduct. 2:1ff. connects the gospel of Christ to our humble deference to/oneness with one another. What we receive in the gospel (2:1), what we see in Christ in the gospel (2:5ff.), should all point believers to humble unity.
 The verb is sun-ath-le-ō (συναθλέω) which means to "athletecize [ath-le-ō] together [sun]."
 "the faith" is Christian doctrine (cf. Jude 1:3). The full phrase "the faith of the gospel" emphasizes the origins/source of the faith, hence, "what the gospel teaches." The gospel is both the motivator and the goal!
 "conduct yourselves" is the Greek verb po-li-teu-o-mai (πολιτεύομαι) which means "to live as citizens." Paul alludes to this familiar experience of Philippi (a Roman colony) to depict the Christian as a privileged citizen. Believers are citizens, that is, members of a privileged community. And there is a shared/community conduct expected of these citizens of heaven (cf. 3:20, "our citizenship [cognate of this verb] is in heaven").
 They caused them "to suffer" (1:29).
 Verse 28 forms the second verbal modifier to "you are standing firm." The two modifiers read: "striving together… and [NASB omits this conjunction] not being intimidated…"
 "in no way alarmed" is literally "not being intimidated [this is the Greek verb ptu-rō (πτύρω)]."
 Greek grammar here clarifies that this is a sign for the opponents of: their destruction and our salvation.
 "the same conflict which you saw in me [in Philippi, per Acts 16:23], and now hear [to be] in me [in Rome]."
 "grant" is cha-ri-zo-mai (χαρίζομαι) which means "to give freely," a cognate of "grace"—cha-ris (χάρις).
 Like Jesus said: "I chose you out of the world, because of this the world hates you" (John 15:19).