Hebrews 9:15-22 (ESV)
Therefore he is the mediator of a new covenant, so that those who are called may receive the promised eternal inheritance, since a death has occurred that redeems them from the transgressions committed under the first covenant.  For where a will is involved, the death of the one who made it must be established.  For a will takes effect only at death, since it is not in force as long as the one who made it is alive.  Therefore not even the first covenant was inaugurated without blood.  For when every commandment of the law had been declared by Moses to all the people, he took the blood of calves and goats, with water and scarlet wool and hyssop, and sprinkled both the book itself and all the people,  saying, "This is the blood of the covenant that God commanded for you."  And in the same way he sprinkled with the blood both the tent and all the vessels used in worship.  Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins.
Hebrews 9:15-20 is probably the best illustrator of the futility in translating the word diatheke as covenant. Here even the reformed with all the works righteousness they want to impose upon us and bind our consciences with, must bow to the true meaning of the word, WILL, TESTAMENT. It makes no sense how they translate this section. They are clods who stay with covenant until they are confronted with:” For where a will is involved, the death of the one who made it must be established.  For a will takes effect only at death, since it is not in force as long as the one who made it is alive.” The word they translate will here, is translated covenant throughout the rest of it. It also makes us consider that even the first “covenant” was really a testament, since it too was inaugurated with blood. The problem was for all the blood that inaugurated the Testament, and all the blood that sustained the Testament it could not be consummated until it was the blood of the God man that was shed for the forgiveness of sins. This is why Christ had to die, there is no forgiveness of sins without the shedding of blood. That means neither can your sins be forgiven with your futile works, offerings, and prayers, there must be blood.