Jesus’ death and resurrection carry no weight apart from his righteous life; always faithful, always trusting in the promises of God. Verses like Romans 8:29 make little sense without it,“For those whom God foreknew He also predestined to be conformed to the image of His Son.”
Those 40 days in the dessert without food, facing temptation from the devil, are a microcosm of Jesus’ entire life, for it is not as if these were the only times he faced temptation as a man, much less directly from the devil, or that somehow the rest of his life was a cakewalk. They are also a microcosm of the righteous life that would be given to us so that we could conform to the image of the Son. We have no righteousness of our own apart from the righteous life of Jesus.
Israel was rebellious and faithless for 40 years in the desert; Jesus was faithful and righteous for 40 days (a true picture of His righteousness)! We rejoice in His righteousness for in it we not only are afforded forgiveness(by way of the cross) but also His holiness.