Your question, What is the Power that works within us? You referenced the following scripture. Ephesians 3:20 ASV - 20 Now unto him that is able to do exceeding abundantly above all that we ask or think, according to the power that worketh in us. The apostle doesn’t delve into the specifics of the power that resides within us. He likely assumed that his readers comprehended his intended meaning where all understanding originates from. To understand what he meant requires wisdom. It requires to see things through the eyes of the Holy Spirit. The understanding is this. The Lord has made us his temple. The Father, the Son and Holy Spirit abides in us. It is through the operation of the Holy Spirit that is in us the power from within. As John wrote 1 John 4:4 “Greater is **he that is in you, than he that is in the world" John is assuring believers that the Holy Spirit within them is more powerful than any opposing forces in the world. It is through the Holy Spirit that we gain the power to conquer the world by embodying his fruits, which are divine attributes and originate from above.