Paul continues to give attention to the Philippians' generosity in these verses (4:10-20) and points out: 1) their uniqueness (in supporting him), 2) their reward (from God) and 3) God's provision (to meet their needs). Paul then concludes his letter with final words of greeting and one last prayer (4:21-23).
Uniqueness (15-16): The Philippian church is a real stand-out. They are the only church that financially supported Paul at the beginning of his ministry beyond Macedonia. They send a gift to meet his needs 2+ times during his stay in Thessalonica. Also, they are fully aware that they are the only ones doing this. But they don't let this fact bother them. Instead, they funnel their energy toward positively advancing the gospel and caring for the dear apostle. It matters not what others are doing or not doing. Like the Lord said, "It is more blessed to give than to receive" (Acts 20:35).
Reward (17-18): Paul then puts to rest any notion that he is flattering them to garner more financial support. In fact, he refuses any further aid: "I have an abundance; I am amply supplied." Paul's desire, instead, is for their reward: "I seek for the profit which increases to your account." With this, he turns their attention to what this gift is in the sight of God. It is "a fragrant aroma, an acceptable sacrifice, well-pleasing to God." Pleasing God is what counts, and He takes notice of their sacrifice and keeps enlarging their account!
Provision (19-20): Now, the Philippians do not give out of a surplus. They give in the midst of their own needs. Hence, Paul hastens to assure them that God will meet all their needs. Paul is sure of this because he knows the God whom they have pleased. He is "my God," and He is generous. And so Paul confidently declares "my God will supply." Paul is also certain of His bountiful care toward His own people and children. He provides "according to His riches in glory in Christ Jesus." Then as he considers this magnificent glory, he breaks out in praise: To Him "be the glory forever and ever." Now, doxologies like this acknowledge the glory God already possesses. With this statement Paul affirms this reality, and then he heartily confirms it with an "Amen."
Greetings (21-23): Paul concludes his letter with greetings. At the very top of his list is the call for the church to greet "every saint in Christ Jesus." No saint should ever be left out in this expression of warmth. Paul then sends greetings from his companions and even from saints from Caesar's household! Finally, he ends with a prayer that the Lord's favor would be with the whole church. To the very end, the church is seen as one spiritual entity and dear to Christ.
 This is the meaning of "giving and receiving" in 4:15. This is then explained as "gift … for my needs" in 4:16.
 They supported Paul in his ministry ever since the Philippian magistrates had him leave their city (cf. Acts 16:37-40) nearly 10 years prior. They also cared for him while he was in Philippi (cf. Acts 16:15, 34).
 "More than once" is, of course, 2+ times.
 Cf. 4:15 ("You yourselves also know… no church shared with me … but you alone").
 Cf. 2 Cor. 8:3-4. As one of "the churches of Macedonia" (2 Cor. 8:1), the Philippians even begged to participate in giving to meet the needs of others.
 "Increases" is imperfective and depicts continual growth like accrued interest. The compounding increase is likely the reward of expanding gospel impact through the preacher whom they supported (cf. 1:12-15).
 There was another time like this. Cf. 2 Cor. 8:1-3.
 "Needs [chrei-a (χρεία)]" is the same word as Paul's "needs" (4:16). Epaphroditus conveyed to him their poor financial situation, but this need is comprehensive ("all"), suggesting more than material needs alone.
 "Our God and Father" highlights both sides of our relationship. We are His worshippers and His children.
 Of the 16 doxologies in the NT, only one has a main verb: 1 Peter 4:11. There, the verb simply states a fact (indicative): "to whom belongs [literally, "is/are," from the Greek ei-mi (εἰμί)] the glory and dominion."
 An "amen" often follows a doxology to heartily confirm/agree with what was just stated. Cf. Rev. 5:13-14.
 "Your" is plural in Greek, referring to the saints, but "spirit" is singular. The church, as one spiritual entity, receives grace from Christ. The church is one, even as its unity was promoted earlier in the book (1:27; 4:2-3).