Can you commit the unpardonable sin in your mind?

All deliberate sins are first committed in the heart and mind.

Mark 7:20-21
“And then he added, “It is what comes from inside that defiles you. For from within, out of a person’s heart, come evil thoughts, sexual immorality, theft, murder, adultery, greed, wickedness, deceit, lustful desires, envy, slander, pride, and foolishness. All these vile things come from within; they are what defile you.”

That’s why it’s important to turn to Jesus Christ to perform heart circumcision, so it’s transformed into thinking, desiring, and doing things that please Him.

Ezekiel 36:25-27
“Then I will sprinkle clean water on you, and you will be clean. Your filth will be washed away, and you will no longer worship idols. And I will give you A NEW HEART, and I will put A NEW SPIRIT in you. I will take out your stony, stubborn heart and give you a tender, responsive heart. And I will put MY SPIRIT IN YOU so that you will follow my decrees and be careful to obey my regulations.”

2 Corinthians 3:3-6
“Clearly, you are a letter from Christ showing the result of our ministry among you. This “letter” is written not with pen and ink, but WITH THE SPIRIT OF THE LIVING GOD. It is carved not on tablets of stone, but ON HUMAN HEARTS.
We are confident of all this because of our great trust in God through Christ. It is not that we think we are qualified to do anything on our own. Our qualification comes from God. He has enabled us to be ministers of HIS NEW COVENANT. This is a covenant not of written laws, but of the Spirit. The old written covenant ends in death; but under the new covenant, THE SPIRIT GIVES LIFE.”

Romans 8:5-8
“Those who are dominated by the sinful nature think about sinful things, but those who are controlled by the Holy Spirit think about things that please the Spirit. So letting your sinful nature control your mind leads to death. But letting the Spirit control your mind leads to life and peace. For the sinful nature is always hostile to God. It never did obey God’s laws, and it never will. That’s why those who are still under the control of their sinful nature can never please God.”

Learn more: Definition of Sin