Its rather easy. God is infinite and eternal but not continually doing something He has deemed complete per His plan.
Genesis 2:1 Thus the heavens and the earth and all their array were completed. 2 On the seventh day God completed the work he had been doing; he rested on the seventh day from all the work he had undertaken.
So you see, Gods plan for redemption through the sacrifice of Jesus on the Cross was completed and does not need to be continually sacrificed. Not limited by time and space but does complete His purposes.