I remembered the quote that if you want to discredit Christianity, you need to attack the Deity of Jesus Christ first. Some cults say that the Trinity is a pagan idea and the word does not appear in the Bible but it does in the word "Godhead". When cults try to dismiss the truth of the Trinity, they take the Scriptures out of context or twist the meaning of the Scriptures. It is no wonder why a lot of them refuse to let the people read the Bible for themselves.
The wonderful, glorious truth of the Trinity has been defended even in the Old Testament. The Spirit of the LORD is none other than the Holy Spirit. Genesis 1:26 has God saying, "And let Us make man in our image, after our likeness and let them have dominion over the fish of the sea and over the fowl of the air, and over the cattle and over all the Earth and over every creeping thing that creepeth upon the Earth." John verifies the Trinity when He writes in John 1:1-13 saying, "In the beginning was the Word, and the Word was with God and the Word was God. The same was in the beginning with God. All things were made by Him and without Him was not an thing made that was made." It would never be angels because angels do not create anything at all. The Apostle John verified the Deity of Christ by affirming that Jesus is the Word and in John 1:10-14 saying, "He was in the world and the world was made by Him, and the world knew Him not. He came unto His own and His own received Him not. But as many as received Him to them gave He power to become the sons of God, even to them that beleive on His name; which were born not of blood nor of the will of the flesh, nor of the wil of man but of God. And the World was made flesh and dwelt among us (and we beheld His glory, the glory as of the only begotten of the Father), full of grace and truth."
The Incarnation of Christ fully involved the work of the Trinity. John 3:16 says, "For God so loved the world that He gave His only begotten Son that whosoever believeth in Him should not perish but have everlasting life." The Holy Spirit took part in the incarnation as Matthew 1:20 says, "But while he thought on these tings, behold the angel of the LORD appeared unto Him in a dream saying, Joseph thou son of David, fear not to take unto thee Mary thy wife for that which is conceived in her is of the Holy Ghost." Luke 1:35 has Mary being told by the angel Gabriel saying, "The Holy Ghost shall come upon thee and the power of the Highest shall overshadow thee: therefore also that holy thing whichs hall be born of thee shall be called the Son of God." The Trinity was made manifest when Jesus got baptized by John the Baptist. Matthew 3:13-17, Mark 1:9-11 and Luke 3:21-23 record the revelation. The Holy Spirit descended like a dove above Jesus and the Father says, "This is My Son with whom I am well-pleased." Some people might say that the Son and the Spirit were created but Genesis 1:2 shows the Holy Spirit has been there, in Genesis 1:16 and John 1:1-14 shows that Jesus Christ is the Word and He is the Second Person of the Trinity.
When the Father gave His Son in John 3:16, it was out of concern for people. The Father would give His Son for the salvation of mankind which attaches the severe warning that whoever rejects the Son also rejects the Father (Luke 10:16). Isaiah 53 is about the Suffering Servant, the Lord Jesus Christ who became the sin sacrifice for mankind. The Father gave His Son to die for our sins as Jesus who knew no sin became sin for us (2 Corinthians 5:21). Jesus died for the sins of mankind in order to redeem them. The Holy Spirit's role in Romans 8:11 says, "But if the Spirit of him that raised up Jesus from the dead dwell in you, He that raised up Christ from the dead shall also quicken your mortal bodies by His Spirit that dwelleth in you." John 16:7-13 declares that the Holy Spirit would be the Comforter, He will reprove the world of sin, and of righteousness and of judgment, of sin because of unbelief, of righteousness because Jesus will go to the Father and of judgment because Satan is judged. It is by the Holy Spirit that guides the believer to truth and the conviction of sin is not only before salvation but also as the Christian grows in grace.