Literally, “because of the blood,” or “on the basis of the blood.” The saints overcame because of the victory of Calvary. For the significance of the “blood” see on Rev. 1:5; cf. on Rom. 5:9.
They overcame.
The mind of the prophet is absorbed in contemplation of those who have been accused by the instigator of evil. He thinks of how they have suffered, and the indignities to which they have been exposed. He remembers how amid hardships they overcame, not in their own strength, but “by the blood of the Lamb.”