by James Montgomery Boice
...if the death of Christ on the cross is the true meaning of the Incarnation, then there is no gospel without the cross. Christmas by itself is no gospel. The life of Christ is no gospel. Even the resurrection, important as it is in the total scheme of things, is no gospel by itself. For the good news is not just that God became man, nor that God has spoken to reveal a proper way of life for us, or even that death, the great enemy, is conquered. Rather, the good news is that sin has been dealt with (of which the resurrection is a proof); that Jesus has suffered its penalty for us as our representative, so that we might never have to suffer it; and that therefore all who believe in him can look forward to heaven. ...Emulation of Christ's life and teaching is possible only to those who enter into a new relationship with God through faith in Jesus as their substitute. The resurrection is not merely a victory over death (though it is that) but a proof that the atonement was a satisfactory atonement in the sight of the Father (Rom 4:25); and that death, the result of sin, is abolished on that basis.
Any gospel that talks merely of the Christ-event, meaning the Incarnation without the atonement, is a false gospel. Any gospel that talks about the love of God without pointing out that his love led him to pay the ultimate price for sin in the person of his Son on the cross is a false gospel. The only true gospel is of the 'one mediator' (1 Tim. 2:5-6), who gave himself for us.
Finally, just as there can be no gospel without the atonement as the reason for the Incarnation, so also there can be no Christian life without it. Without the atonement the Incarnation theme easily becomes a kind of deification of the human and leads to arrogance and self advancement. With the atonement the true message of the life of Christ, and therefore also of the the life of the Christian man or woman, is humility and self sacrifice for the obvious needs of others. The Christian life is not indifference to those who are hungry or sick or suffering from some other lack. It is not contentment with our own abundance, neither the abundance of middle class living with home and cars and clothes and vacations, nor the abundance of education or even the spiritual abundance of good churches, Bibles, Bible teaching or Christian friends and acquaintances. Rather, it is the awareness that others lack these things and that we must therefore sacrifice many of our own interests in order to identify with them and thus bring them increasingly into the abundance we enjoy... We will live for Christ fully only when we are willing to be impoverished, if necessary, in order that others might be helped.'
Excerpt from Foundations of the Christian Faith