When Christ was sent to the world He was sent by both the Father and the Holy Spirit according to Isaiah 48:16 “Come ye near unto me, hear ye this; I have not spoken in secret from the beginning; from the time that it was, there am I: and now the Lord GOD, and his Spirit, hath sent me.”

Isn't this a clear proof of the trinity?

Answer:

A very brief look at the verse in the original language tells us that it has been mistranslated and misunderstood. Here is the same verse in a few other translations:

“and now the Lord God has sent me, and given me his spirit.” (Bible in Basic English)
“And now the Lord GOD has sent me and his Spirit.” (Revised Standard Version)
“And now the Lord Jehovah hath sent me, and His Spirit.” (Young‟s Literal Translation)

According to the context the speaker appears to be Christ. It was God the Father who sent Jesus on His mission (John 3:16). When Jesus entered the world as the Messiah, God sent His Holy Spirit to rest upon Him (Isaiah 11:2; 42:1; 61:1–3; Matthew 3:16; Luke 4:18–21; John 1:32, 33; Acts 10:38). In this
text Christ is simply saying that God the Father sent me and has anointed me with His Spirit. There was only one sender (the Father) not two. This is confirmed in numerous places (John 5:30,36,37; 6:39,44,57; 8:16,18,29,42; 12:49; 14:24; 17:21,25; 20:21; Galatians 4:4-6; 1 John 4:10, 14;).