When Jesus opened up the Bible for the disciples’ understanding on the road to Emmaus, he summed it up in the following way:
45 Then he opened their minds to understand the Scriptures, 46 and said to them, “Thus it is written, that the Christ should suffer and on the third day rise from the dead, 47 and that repentance and forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem.
So, according to Jesus (and I would say he is a good authority) the Bible is summed up in two themes: 1) Jesus and 2) that repentance and forgiveness of sins should be proclaimed in his name to all nations.
If you are a Christian, it’s about Jesus and the nations. Here is scripture to meditate on regarding the Great Commission throughout the Bible:
12 The Lord had said to Abram, “Go from your country, your people and your father’s household to the land I will show you.
2 “I will make you into a great nation,
and I will bless you;
I will make your name great,
and you will be a blessing.
3 I will bless those who bless you,
and whoever curses you I will curse;
and all peoples on earth
will be blessed through you.”
16 But I have raised you up for this very purpose, that I might show you my power and that my name might be proclaimed in all the earth.
5 See, I have taught you decrees and laws as the Lord my God commanded me, so that you may follow them in the land you are entering to take possession of it. 6 Observe them carefully, for this will show your wisdom and understanding to the nations, who will hear about all these decrees and say, “Surely this great nation is a wise and understanding people.”
10 He says, “Be still, and know that I am God;
I will be exalted among the nations,
I will be exalted in the earth.”
1 May God be gracious to us and bless us
and make his face shine on us—
2 so that your ways may be known on earth,
your salvation among all nations.
6 he says:
“It is too small a thing for you to be my servant
to restore the tribes of Jacob
and bring back those of Israel I have kept.
I will also make you a light for the Gentiles,
that my salvation may reach to the ends of the earth.”
14 For the earth will be filled with the knowledge of the glory of the Lord
as the waters cover the sea.
14 And this gospel of the kingdom will be preached in the whole world as a testimony to all nations, and then the end will come.
18 Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. 19 Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.”
42 At daybreak, Jesus went out to a solitary place. The people were looking for him and when they came to where he was, they tried to keep him from leaving them. 43 But he said, “I must proclaim the good news of the kingdom of God to the other towns also, because that is why I was sent.”
8 But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.”
13 Christ redeemed us from the curse of the law by becoming a curse for us, for it is written: “Cursed is everyone who is hung on a pole.” 14 He redeemed us in order that the blessing given to Abraham might come to the Gentiles through Christ Jesus, so that by faith we might receive the promise of the Spirit.
20 It has always been my ambition to preach the gospel where Christ was not known, so that I would not be building on someone else’s foundation.
9 After this I looked, and there before me was a great multitude that no one could count, from every nation, tribe, people and language, standing before the throne and before the Lamb. They were wearing white robes and were holding palm branches in their hands.