"that Yahweh might do according to the message that he told Ahijah the Shilonite to tell Jeroboam son of Nebat" or "that Yahweh might do what he had said he would do when he told Ahijah the Shilonite to give a message to Jeroboam son of Nebat"
# his word that Ahijah the Shilonite had spoken to Jeroboam son of Nebat
This refers to the message that God gave Ahijah to tell Jeroboam.