An excerpt from a sermon on John 17:1; Psalm 45:7 found in the book Christ For Us
The whole human nature of the Redeemer consisting of soul and body has by the rewarding grace of the Father been rendered immortal and eternally infallible. This is the first element of the Saviour's glory and is necessarily presupposed in all others. And that this element is a real gift of God is obvious if you consider that the humanity of Jesus is but a creature and must like all other creatures partake of that defect or want of self-sufficiency which is the special mark of distinction between everything created and the Creator. No creature can be self-sufficient, for to be self-sufficient is to have the cause of existence, and therefore the cause of continuance, in one's self which can be affirmed of none but the Creator only. Hence no creature can be immortal except by the will and power and gift of the Creator. Adam had no claim on God to continue life to him for one moment, and the benevolence of the covenant of works appears in this, that, in return for a service which Adam was bound to render in any event, God freely obliged himself to give his creature immortality. The human nature of the second Adam is in itself as destitute of self-sufficiency as that of the holy first Adam. Its sufficiency is of God, and because Jesus had fulfilled the conditions which Adam failed to fulfil he has gained, with other blessings, this for himself, that his human nature shall be immortal and shall not see death. Thus Jesus dieth no more and the glory of immortality is a necessary element of his great reward. But besides immortality his human nature has obtained also an everlasting infallibility. This also, if possessed at all, must be a blessing communicated. For just as no creature is self-sufficient or adequate for its own preservation in being, so no creature is infallible or adequate to its own preservation in rectitude. Thus, in this sense of inherent, essential, self-derived attributes there is none good but God. And this statement, made by Jesus to the young man, was most appropriate, for Jesus, while possessed of Godhead, himself very God, saw that this young man recognized nothing but his humanity which, like every other creature, possessed no essential infallible quality of moral rectitude. Nothing but grace can preserve any creature from falling, and from its very nature grace is a thing which God is not bound to bestow. Therefore holy angels have fallen and holy man hath fallen too from their high original and created estate. Had Adam fulfilled the terms of the covenant under which he had been placed he would have merited confirming grace which would have rendered him infallibly righteous and blessed along with all his posterity.
What the first Adam failed to do the second Adam accomplished, and therefore does he merit and obtain for his human nature those communications of confirming grace in virtue of which the glorified humanity of Jesus shall never fall from righteousness, but it shall ever be true of his human nature, 'thou hast loved righteousness and hated wickedness.' It is quite true we do very commonly contemplate this truth as a very certain truth - that the human soul and body of Jesus will ever abide in the love and practice of all holiness, but we do not sufficiently attend to the cause of this. We look upon it as a matter of fact, but we look upon it improperly as a matter of course. It is not so. There is nothing in the human nature of Jesus in itself considered to keep it from falling. In this world it was created holy by an exercise of the power of the Holy Ghost - and preserved holy by the same Spirit given to him without measure - and, having finished the work given him to do, he is rewarded in part by an everlasting, unfailing infallibility conferred upon him by the Father. Conferred, I say, for I beg to remind you again that this infallibility is no matter of course, any more than the immortality. Both are communicated, and each forms a part of that glory which Jesus has gained as Mediator. The possession of immortality and infallibility by the human nature of Emmanuel is a portion of his reward, and could not have been communicated unless Jesus had fulfilled all righteousness.
Indeed, unless Jesus had stood to all his stipulated promises in the covenant, neither of them could have been his. Immortality could not have been his, for his resurrection is a proof of the completeness of his work. And infallibility could not have been his, for such a failure or withdrawal would of itself have been an exhibition of fallibility. Jesus, however, having accomplished all that the Father had given him to do, was raised from the dead, being quickened of the Spirit. His body was not left to see corruption nor his soul left in the state of the dead, but as God's Holy One, now infallibly holy by his Father's rich grace, he was received as he who was dead but is alive again and dieth no more. Not that his human nature has in itself any essential property corresponding to these things, but only because in Christ's communicated glory this forms part, namely that his human nature should be anointed with undying strength and grace sufficient to give holiness infallible. 'He asked life of thee, and thou gavest it him, even length of days for ever and ever' - natural immortality - 'and through the mercy of the most High he shall not be moved' - a promise of a spiritual and moral infallibility through grace.