Here is an interesting and insightful excerpt from Stephen Charnock’s two volume set The Existence and Attributes of God (Volume 1) pp 345-346:
God always acts according to the immutable nature of his holiness, and can no more change in his affections to good and even, than he can in his essence…The will of God is unchangeably set to love righteousness and hate iniquity, and from this hatred to punish it; and if a righteous creature contracts the wrath of God, or a sinful creature hat the communications of God’s love, it must be by a change in themselves. Is the sun changed when it hardens one then and softens another, according to the disposition of the several objects? Or when the sun makes a flower more fragrant, and a dead carcass more noisome? There are divers effects, but the reason of that diversity is not in the sun, but in the subject; the sun is the same, and produceth those different effects by the same quality of heat; so if an unholy soul approach to God, God looks angrily upon him; if a holy soul come before him, the same immutable perfection in God draws out his kindness towards him: as some think, the sun would rather refresh than scorch us, if our bodies were of the same nature and substance with that luminary. As the will of God for creating the world was no new, but an eternal will, though it manifested itself in time, so the will of God for the punishment of sin, or the reconciliation of the sinner, was no new will: though his wrath in time break out in the effects of it upon sinners, and his love flows out in the effects of it upon penitents. Christ by his death did what was consonant to his eternal will; he come not to change his will but to execute his will: “Lo, I come to do they will, O God” (Heb. x. 7). And the grace of God in Christ was not a new grace, but an old grace in a new appearance; “the grace of God hath appeared” (Tit. i. 11).