The all important (Great) final instructions (Commission) Jesus gave to his disciples.
Preach the gospel to everyone:
Mark 16:15
And he said unto them, Go ye into all the world, and preach the gospel to every creature.
Baptize new believers and teach them to obey and follow the word of God:
Matthew 28:19-20
Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: [20] Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
Be a witness of Jesus Christ everywhere:
Acts 1:8
But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth.
This commission is to be carried out by every Christian, it is to ensure the preservation of the faith and that souls will continue to be saved and glorify the Lord Jesus Christ until he returns. God has committed to every believer the word of reconciliation to bring unsaved men and God back together through the truth of the gospel.
2 Corinthians 5:18-20
And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation; [19] To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation. [20] Now then we are ambassadors for Christ, as though God did beseech you by us: we pray you in Christ’s stead, be ye reconciled to God.
1 Timothy 2:4
Who will have all men to be saved, and to come unto the knowledge of the truth