St. John the Baptist is well-known as a biblical prophet who paved the way for Jesus Christ. However, he also had strong words for King Herod, who was engaged in a strange relationship with his niece, Herodias, the wife of his half-brother Philip.
For John said to Herod, “It is not lawful for you to have your brother’s wife.”
At first King Herod was not willing to kill him, as he liked listening to St. John the Baptist.
Herod feared John, knowing that he was a righteous and holy man, and kept him safe. When he heard him, he was much perplexed; and yet he heard him gladly.
While King Herod didn't want to sentence St. John the Baptist to death, Herodias would not stand for it any longer and made a plan to convince Herod.
[W]hen Herodias’ daughter came in and danced, she pleased Herod and his guests; and the king said to the girl, “Ask me for whatever you wish, and I will grant it.” And he vowed to her, “Whatever you ask me, I will give you, even half of my kingdom.” And she went out, and said to her mother, “What shall I ask?” And she said, “The head of John the baptizer.” And she came in immediately with haste to the king, and asked, saying, “I want you to give me at once the head of John the Baptist on a platter.”
Herod reluctantly gave in to her request and ultimately beheaded St. John the Baptist because of Herodias' influence.