Acts 10:14 But Peter said, “Not so, Lord! For I have never eaten anything common or unclean.” 15 And a voice spoke to him again the second time, “What God has cleansed you must not call common.”

Stronghold are a set of knowledge that has become a force that drives your life. They are subconscious operating systems in men that make them acts in certain ways even when they don't like it. Stronghold is not easy to break without a deliberate actions using the word of God. 

These stronghold are patterns or a set of thoughts, ideas, inner argument that stands against our spiritual experience. They are like fortified places where evil forces or harmful beliefs are entrenched and from which they exert influence, requiring divine power to demolish them. These stronghold are built over a period of time through words and cultures. 

Stronghold stand against God's program and agenda most times. God visited Peter in a vision about His next agenda on earth and for his ministry, but Peter could not receive it because of religious stronghold. Though he was aware that this is God's agenda, he could not enter into it because of stronghold. Only God's word can break, demolish cast them down. 

II Corinthians 10:4 For the weapons of our warfare are not carnal but mighty in God for pulling down strongholds, 5 casting down arguments and every high thing that exalts itself against the knowledge of God, bringing every thought into captivity to the obedience of Christ. 

Olanrewaju Niyi