Thomas Aquinas, Compendium of Theology

Christ recovered for the human race not merely what Adam had lost through sin, but all that Adam could have attained through merit. For Christ's power to merit was far greater than that of man prior to sin. By sin Adam incurred the necessity of dying, because he lost the power which would have enabled him to avoid death if he had not sinned. Christ not only did away with the necessity of dying, but even gained the power of not being able to die. Therefore His body after the resurrection was rendered impassible and immortal. Thus Christ's body was not like that of the first man, which had the power not to die, but was absolutely unable to die. And this is what we await in the future life for ourselves.

Another consideration: Christ's soul before His death was capable of suffering in company with the suffering of His body. Consequently, when His body became incapable of suffering, His soul also became incapable of suffering.

Furthermore, the mystery of man's redemption was now accomplished. To enable Christ to achieve that end, the glory of fruition had, in God's dispensation, been restricted to the higher regions of His soul, so that no overflowing to the lower parts and to the body itself would occur, but each faculty would be allowed to do or suffer what was proper to it. But now the body and the lower powers were wholly glorified by an overflow of glory from the higher regions of the soul. Accordingly Christ, who before the passion had been a comprehensor because of the fruition enjoyed by His soul and a wayfarer because of the passibility of His body, was now, after the resurrection, no longer a wayfarer, but exclusively a comprehensor.