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Isaiah 50:4 The Lord GOD has given Me The tongue of the learned, That I should know how to speak A word in season to him who is weary. He awakens Me morning by morning, He awakens My ear To hear as the learned.
When God commissioned Moses to deliver Israel from Egypt, Moses made the excuse that his ability to communicate wouldn’t be up to the job.
Exodus 4:10 Then Moses said to the LORD, "O my Lord, I am not eloquent, neither before nor since You have spoken to Your servant; but I am slow of speech and slow of tongue."
To which God replied:
Exodus 4:11 So the LORD said to him, "Who has made man’s mouth? Or who makes the mute, the deaf, the seeing, or the blind? Have not I, the LORD? 12 "Now therefore, go, and I will be with your mouth and teach you what you shall say."
When God through Moses prophesied of the greater prophet to come he said:
Deuteronomy 18:18 ‘I will raise up for them a Prophet like you from among their brethren, and will put My words in His mouth, and He shall speak to them all that I command Him. 19 ‘And it shall be that whoever will not hear My words, which He speaks in My name, I will require it of him.
That prophet who would speak the words of God is Jesus.
Acts 3:22 "For Moses truly said to the fathers, ‘The LORD your God will raise up for you a Prophet like me from your brethren. Him you shall hear in all things, whatever He says to you. 23 ‘And it shall be that every soul who will not hear that Prophet shall be utterly destroyed from among the people.’
Isaiah 50:4 is a Messianic prophecy and the words are Christ’s. His God-given capacity to understand scripture and to speak from it was apparent by the age of 12.
Luke 2:41 His parents went to Jerusalem every year at the Feast of the Passover. 42 And when He was twelve years old, they went up to Jerusalem according to the custom of the feast... 46 Now so it was that after three days they found Him in the temple, sitting in the midst of the teachers, both listening to them and asking them questions. 47 And all who heard Him were astonished at His understanding and answers.
When he began his ministry the people marvelled at both his understanding of scripture and the way he spoke. At Nazareth he picked up another prophecy of Isaiah and applied it to himself.
Luke 4:17 And there was delivered unto him the book of the prophet Esaias. And when he had opened the book, he found the place where it was written, 18 The Spirit of the Lord is upon me, because he hath anointed me to preach the gospel to the poor; he hath sent me to heal the brokenhearted, to preach deliverance to the captives, and recovering of sight to the blind, to set at liberty them that are bruised, 19 To preach the acceptable year of the Lord. 20 And he closed the book, and he gave it again to the minister, and sat down. And the eyes of all them that were in the synagogue were fastened on him. 21 And he began to say unto them, This day is this scripture fulfilled in your ears. 22 And all bare him witness, and wondered at the gracious words which proceeded out of his mouth. And they said, "Is this not Joseph’s son?"
The words and doctrine were God’s.
John 7:15 And the Jews marveled, saying, "How does this Man know letters, having never studied?" 16 Jesus answered them and said, "My doctrine is not Mine, but His who sent Me. 17 "If anyone wants to do His will, he shall know concerning the doctrine, whether it is from God or whether I speak on My own authority.
John 12:49 For I have not spoken of myself; but the Father which sent me, he gave me a commandment, what I should say, and what I should speak.
The officers sent to arrest him testified:
John 7:46 The officers answered, "No man ever spoke like this Man!"
Isaiah 50:4 is a prophecy of the eloquence and understanding which God would manifest in his son.
Psalms 45:2 You are fairer than the sons of men; Grace is poured upon Your lips; Therefore God has blessed You forever.
AV Matthew 17:5 While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear ye him.
I hope this helps.