Today's Hymn tells about the Blood of Jesus, which was the price He paid to redeem (save) those who trust in Him as God and Savior.
A blood (i.e. death) sacrifice is required because without the shedding of blood, there is no remission of sin.
Jesus provided His own death (blood sacrifice) as the payment for the sins of anyone who trusts in Him and accepts His substitute sacrifice in place of the death penalty he or she will have to personally pay if they do not accept His sacrificial gift of salvation.
HERE'S THE LINK TO There is a fountain filled with blood
