For we affirm that the divine nature is undoubtedly incapable of suffering, and cannot in any sense be brought low from its exalted standing, and cannot labour with difficulty over what it wishes to do. But we say that the Lord Jesus Christ is true God and true man, one person in two natures and two natures in one person. In view of this, when we say that God is suffering some humiliation or weakness, we do not understand this in terms of the exaltedness of the non-suffering nature, but in terms of the weakness of the human substance which he was taking upon himself.... For we are not, in this way implying lowliness on the part of the divine substance, but are making plain the existence of a person comprising God and man, (Anselm of Canterbury: The Collected Works, Oxford, 2008, p. 274-275.
Note that Anselm does not merely say that the human nature of Jesus suffered for us, but that the person of the Son, impassible in his deity, suffered for us in his human nature. What we need from God is not the sympathy of a cosmic fellow-sufferer, but one who has acted to save us from sin and suffering. Only a suffering God in Christ can help us. Calvary reveals the true the depths of God's limitless, unchanging love for sinners, Romans 5:6-8. Impassible love is not needy and vulnerable, but free and outgoing; flowing from the Father, through the Son and by the Spirit to the world.
As the Puritan Poet Edward Taylor (c1642-1729) meditated,
What Love is this of thine, that Cannot bee
In thine Infinity, O Lord, Confinde,
Unless it in thy very Person see,
Infinity, and Finity Conjoyn'd?
What hath thy Godhead, as not satisfide
Marri'de our Manhood, making it its Bride?
Oh, Matchless Love! filling Heaven to the brim!
O're running it: all running o're beside
This World! Nay Overflowing Hell; wherein
For thine Elect, there rose a mighty Tide!
That there our Veans might through thy Person bleed,
To quench those flames, that else would on us feed.
Oh! that thy Love might overflow my Heart!
To fire the same with Love: for Love I would.
But oh! my streight'ned Breast! my Lifeless Sparke!
My Fireless Flame! What Chilly Love, and Cold?
In measure small! In Manner Chilly! See.
Lord blow the Coal: Thy Love Enflame in mee.