How do we know John the Baptist was a true prophet?

John the Baptist's authenticity as a prophet is confirmed through his unwavering testimony about Christ. In John 1:20-23, John openly denies any claims of being the Christ or a great prophet, demonstrating his humility and commitment to God's glory. He identifies himself simply as a voice sent to prepare the way for the Lord, enhancing his credibility as a true prophet of God. By consistently directing attention to Jesus and acknowledging his unworthiness, he embodies the essence of prophetic ministry, which is to exalt God and lead others to Him.