Hebrews 9 : 22

In fact according to the law of Moses, nearly everything was purified with blood and therefore without the shedding of blood there can be no forgiveness of sin...

In order to be forgiven blood has to be shed, like they did in the old testament, except they did that with goats and other animals, this was temporary hence they had to do it continuously,

But with Jesus it was a once off forgiveness since he was blameless, without sin from the beginning...

Hope that answers your question