While reading F. F. Bruce’s commentary on Galatians, I came across an excursus on “the Gospel.” Before giving my own comments, read Bruce’s explanation of what the Gospel is.
In the NT the εὐαγγέλιον [“gospel”] is (a) the proclamation by Jesus that the kingdom of God has drawn near; (b) the proclamation by the disciples that in Jesus the kingdom of God is fully manifested, that he by his humiliation and exaltation is set forth as Messiah, Lord, Son of God. The second phase of the εὐαγγέλιον arises necessarily out of the first: the passion and triumph of Jesus, which formed the basis of the apostolic preaching, crowned his ministry and embodied and confirmed all that he had taught about the kingdom of God. O. A. Piper has distinguished ‘two patterns in which the good news is presented, namely the Kingdom type and the Resurrection type’. The difference between them lies ‘in perspective rather than in substance’ (‘Change of Perspective’, INT. 16 , 402–417, especially 416f.).
The background of the substantive εὐαγγέλιον and its related verb εὐαγγελίζουαι [“preach or proclaim the gospel”] as used in the NT, must be sought here and there in Is. 40–66. The good news of Zion’s liberation and restoration, celebrated in Is. 40:9. ὁ εὐαγγελιζόμενος Σειών, ‘O thou that tellest good tidings to Zion’ (cf. Is. 60:6 LXX, τὸ σωτήριον κυρίου εὐαγγελιοῦνται), is interpreted in the NT as adumbrating the good news of a greater liberation and restoration—the salvation procured by Christ. The words of Is. 52:7, ὡς πόδες εὐαγγελιζομένου ἀκοὴν εἰρήνή, ὡς εὐαγγελιζόμενος ἀγαθά, are supplied by Paul in Rom. 10:15 to preachers of the Christian gospel. In Is. 40–66 it is Yahweh himself who is ultimately proclaimed in the good news: the herald is told to ‘say to the cities of Judah, “Behold your God!” ’ (Is. 40:9). So in the NT the bearers of the gospel summarize their commission in words such as these: ‘what we preach is not ourselves, but Jesus Christ as Lord’ (2 Cor. 4:5). This comes close to the Hellenistic usage of the word-group, which has to do with ‘the God-Emperor who is venerated in the cult and the εὐαγγέλιον which proclaims him’ (J. Schniewind, Euangelion, II [Güttersloh, 1931], 183).
Most important of all texts in Is. 40–66 for the NT usage is Is. 61:1, where an unnamed speaker introduces himself by saying, ‘The Spirit of the Lord Yahweh is upon me, because Yahweh has anointed me to bring good tidings to the poor’ (LXX εὐαγγελίσασθαι πτωχοῖς). In Lk. 4:17–19 Jesus is depicted as reading this scripture in the Nazareth synagogue and applying it to himself—newly anointed, ‘made Messiah’, for the proclamation of the gospel. Not only so, but in the earlier ‘Q’ incident of Jesus’ reply to John the Baptist’s message from prison (Lk. 7:22; Mt. 11:5) the fact that ‘the poor have good news preached to them’ (πτωχοὶ εὐαγγελίζονται) is emphasized as the conclusive proof that Jesus is indeed the ‘coming one’ to whom John had pointed forward. 
Note several things based on the use of this term in Scripture:
- Your political views are not “the Gospel.”
- Your theological distinctives (as true and right as they may be) are not “the Gospel.”
- Talking about your church or inviting people to your church is not proclaiming the Gospel. While those are certainly good things to do, this is not what it means to “preach the Gospel.”
- Helping the poor is not proclaiming the Gospel. Preaching “the good news” to the poor is proclaiming the gospel. Likewise, revitalizing communities, seeking social justice, and any number of good things one can do is not the same as “preaching the Gospel.”
- Being a good neighbor and performing deeds in the hope that your neighbor will notice “something different” about you (as it was put during my childhood) is not “proclaiming the Gospel.” You should be a good neighbor because that’s part-and-parcel with being a good Christian, but that’s not proclaiming the Gospel.
John Dickson, in his book The Best Kept Secret of Christian Mission, makes a necessary distinction between “promoting the Gospel” and “proclaiming the Gospel.” Many of the activities listed above certainly may “promote the Gospel” but they are not the same as “proclaiming the Gospel.” Dickson lists six in his book: praying (ch. 4), our giving (ch. 5), through the good works of the church (ch. 6), Christian behavior (ch. 7), public praise (ch. 10), and in daily conversation (ch. 11).
One of the few places where we see the content of the post-resurrection Gospel spelled out is 1 Cor. 15:3-5. Most scholars agree that this passage is earlier than Paul and in it Paul is most likely quoting an early Christian creed or confession. John Dickson, in chapter 8 of his book gives an excellent summary of the Gospel and what the proclamation of the Gospel (whether one-on-one or in a worship setting) must entail: “(1) the sin-atoning death, (2) the burial, (3) the resurrection, (4) and the appearances (5) of the one authenticated by God to be Messiah/Lord.”
So we can say with much certainty that there are five parts to this summary of the Gospel:
- Jesus is the Christ/Messiah/Lord (the concept of the Kingdom is inherent in it)
- Jesus’ death was salvific (that is, for the purpose of saving people)
- Jesus died and was buried
- Jesus rose/was raised from the dead
- Jesus appeared to many after his resurrection and they confirmed his identity
Anything else one preaches is not the Gospel, even if the message is true, right, relevant, and helpful.
To do anything other than proclaim this message, even if the act is true, right, relevant and helpful, is not to preach the Gospel.
 F. F. Bruce, The Epistle to the Galatians: A Commentary on the Greek Text (Grand Rapids: W.B. Eerdmans Pub. Co., 1982).
 F. F. Bruce, The Epistle to the Galatians: A Commentary on the Greek Text (Grand Rapids: W.B. Eerdmans Pub. Co., 1982), 81-82.
 John Dickson, The Best Kept Secret of Christian Mission (Grand Rapids: Zondervan, 2010).
 Dickson, 111-140.