ISB ~ Revelation 6 v9

the altar:The heavenly counterpart to the bronze altar of sacrifice in the Jerusalem Temple (2 Chron 4:1). slain for the word The martyrs bear the likeness of Christ, the slain Lamb (12:11; Mt 23:34-35). Their pleas for justice sound from beneath the altar, recalling how the lifeblood (Lev 17:11) of sacrificial victims was poured out at the base of the Temple altar (Lev 4:7). Martyrdom is thus portrayed as a priestly act of sacrificing one’s life to God (Rom 12:1; Phil 2:17; 1 Pet 2:5).