Question:

Why was it such a sacrifice for god to lose his only son Jesus, when he
has the power to tell the future and knew he would be resurrected?

Answer:

I am guessing that you are not a parent. For me, to imagine watching my
one and only son (I actually have one son by the way) being tortured in
the most horrendous way, rejected by those he poured his life out for, and
rejected by the people he came to die for is difficult to even imagine.
It must have been absolute torture for the Father to hold back and to let
his son be treated in this shameful way. Besides, when Jesus died, he
received on himself the full weight of the responsibility for all the sin
ever committed by every human being. Imagine Jesus experiencing the wrath
of God–of his Father–even for a brief time. The entire scene must have
been excruciatingly painful for both the Father and the Son. This
explains Jesus incredible anguish in Matthew 26: in the garden. It also
explains his agonizing, painful, desperate cry from the cross, “My God,
My God, why have you forsaken me.” The fact that from God’s omnicient
viewpoint he knew the ultimate outcome of this horrendous scene probably
did little to make it easier at the time. It is hard for us humans to
speculate accurately on exactly how God felt, but we can be sure that it
was not fun–it definitely hurt God. God is able to feel emotional pain.
Genesis 6:6 tells us that. I can understand why you, from a human
perspective, do not completely understand how God can feel emotional
pain. Guess what, I do not understand it either, but it is true.

John Oakes