The Trinity of God was revealed by Jesus and documented by the apostles in many books within the New Testament. 

For example, in the Gospel according to Saint Matthew, Our Lord and Saviour had commanded the disciples and apostles to baptise the believers, saying, “Go therefore and make disciples of all the nations, baptising them in the name of the Father and of the Son and of the Holy Spirit” (Matthew 28:19, NKJV). Note that He did not say “names” in the plural but “name” indicating that they are one. 

In the Pauline Epistles, we find Saint Paul referring to the Trinity several times. In giving the blessing, in the second epistle to the Corinthians, he says, “The grace of the Lord Jesus Christ, and the love of God, and the communion of the Holy Spirit be with you all. Amen.” (2 Corinthians 13:14, NKJV) 

Saint Peter referred to the trinity doctrine as well in his first epistle, saying that the believers are “elect according to the foreknowledge of God the Father, in sanctification of the Spirit, for obedience and sprinkling of the blood of Jesus Christ: Grace to you and peace be multiplied.” (1 Peter 1:2, NKJV) 

In the Book of Revelation, Saint John started with reference to the Trinity: “Grace to you and peace from Him who is and who was and who is to come, and from the seven Spirits who are before His throne, and from Jesus Christ, the faithful witness, the firstborn from the dead, and the ruler over the kings of the earth. To Him who loved us and washed us from our sins in His own blood” (Revelation 1:4-5, NKJV) 

Not all verses have been quoted; however, the four scriptures supplied above are more than enough to count as proof. The doctrine of the Trinity is very obvious within the New Testament manuscripts.