All the glory for salvation belongs solely to God, so what else could the Gospel be, what else could the whole of salvation be reliant upon, than that glorious grace of God!!
For this cause the Gospel is called the Glorious Gospel of God or Christ 1 Tim 1:11
According to the glorious gospel of the blessed God, which was committed to my trust.
2 Cor 4:4
In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them.
Gods Glory as He stated is His Sovereignty in showing Mercy on some as He wills Ex 33:17-19
17 And the Lord said unto Moses, I will do this thing also that thou hast spoken: for thou hast found grace in my sight, and I know thee by name.
18 And he said, I beseech thee, shew me thy glory.
19 And he said, I will make all my goodness pass before thee, and I will proclaim the name of the Lord before thee; and will be gracious to whom I will be gracious, and will shew mercy on whom I will shew mercy.
Paul used this in his teaching on sovereign election Rom 9:11-16
11 (For the children being not yet born, neither having done any good or evil, that the purpose of God according to election might stand, not of works, but of him that calleth)
12 It was said unto her, The elder shall serve the younger.
13 As it is written, Jacob have I loved, but Esau have I hated.
14 What shall we say then? Is there unrighteousness with God? God forbid.
15 For he saith to Moses, I will have mercy on whom I will have mercy, and I will have compassion on whom I will have compassion.
16 So then it is not of him that willeth, nor of him that runneth, but of God that sheweth mercy.