"When Moses had proclaimed every commandment of the law to the people, he took the blood of calves, together with water, scarlet wool and branches of hyssop, and sprinkled the scroll and all the people. He said, 'This is the blood of the covenant, which God has commanded you to keep.' In the same way, he sprinkled with the blood both the tabernacle and everything used in its ceremonies. In fact, the law requires that nearly everything be cleansed with blood, and without the shedding of blood there is no forgiveness." NIV translation
In the same way, covenants under the law required the shedding of blood. Like a will, this blood was required for the contract to take effect.
"It was necessary, then, for the copies of the heavenly things to be purified with these sacrifices, but the heavenly things themselves with better sacrifices than these. For Christ did not enter a man-made sanctuary that was only a copy of the true one; he entered heaven itself, now to appear for us in God's presence." NIV translation
The animal sacrifices were sufficient for the earthly temple but a better sacrifice was required to enter heaven itself.
"Nor did he enter heaven to offer himself again and again, the way the high priest enters the Most Holy Place every year with blood that is not his own. Then Christ would have had to suffer many times since the creation of the world. But now he has appeared once for all at the end of the ages to do away with sin by the sacrifice of himself." NIV translation
The high priest had to enter every year to atone for the sins of the people and he could never say it is finished like Jesus did on the cross. He presented Himself once and for all; for all people and for all time.
"Just as man is destined to die once, and after that to face judgment, so Christ was sacrificed once to take away the sins of many people; and he will appear a second time, not to bear sin, but to bring salvation to those who are waiting for him." NIV translation
Just as we do not normally die over and over again, Jesus does not have to go back to the cross over and over again to pay for our sins. He has paid the penalty for sin once and for all but He is coming back to get those who are His. Are you waiting for His return?