Regret (μεταμέλομαι) is caused when someone feels sorry or remorse concerning a previous action. It is not equivalent to repent (μετάνοια), which means to change the mind.
When Paul had to write a letter to the saint in Corinth to correct their unbecoming behavior, he was very poignant in his comments. However, even though Paul was sorry that he had to be so hard, he did not regret writing the letter, 2 Corinthians 7:8. Through the letter, he caused them to grieve; however, this type of grief brings a change of mind, not death, 1 Corinthians 7:10.
In one of His encounters with the leaders of Israel, Jesus speaks of two sons who respond in different ways to their father’s request. The first son refused to work in the vineyard; however, after considering his father’s request, he regretted his response and went to work, Matthew 21:29. The second one agreed with the father’s request but did not go. This was to point out the fact that John the Baptist came to the leaders of Israel in righteousness, and even though they did not receive him, the tax collector and harlots did. Seeing their change of mind in response to John’s message should have opened the leader’s eyes; however, they still did not regret rejecting his message, Matthew 21:32.
Judas Iscariot was a thief, John 12:6. He was the only disciple of the twelve who did not believe that Jesus was the Messiah; however, because he handled the purse, he chose to stay with them. This type of attitude led to betraying Christ for thirty pieces of silver. However, his intent was not for Christ to be put to death; rather, he was expecting them to beat Him and afterward release Him. When He was condemned to death, Judas responded with remorse for his actions and sought to return the money, Matthew 27:3. He knew that Jesus was innocent, and by his hand Christ was placed into a position that allowed the leaders of Israel to have Him put to death, Matthew 27:4. This regret did not result in a change of mind, or repentance; instead, he hung himself, Matthew 27:5, for his grief was not a godly one but due to his loss of income.
Christ is the High Priest after the Melchizedek order. This is a covenant made by the Father that He would never regret. He is the High Priest into the age, Hebrews 7:21. Therefore, Jesus has become a surety of a better covenant. Unlike the Levitical order, which had many High Priests, His priesthood is unchangeable, for He abides into the age, Hebrews 7:24.
The root of regret (μεταμέλομαι) is to care about (μελει). Therefore, when God calls, He does not regret His gift, Romans 11:29, and godly grief produces a change of mind without regret, 2 Corinthians 7:10, for God does not again concern Himself with His actions as to be remorseful in saving.