Fortifying Hearts

Paul says in Ephesians 3:16-17 that he prays for God to strengthen believers, with power, through the Spirit, in the inner man. The goal of this strengthening is so that Christ may dwell in the believers' hearts, not in a literal sense, but in a spiritual sense, "though faith." In other words, believers' hearts must be fortified by God in order for Christ to dwell there in his absence, much like the breech of a rifle or cannon must be stronger than the muzzle in order not to rupture at the explosion that takes place inside it.