purged - purified by judgments; destroying the ungodly, correcting and refining the godly.
blood - (Isa 1:15).
spirit - Whatever God does in the universe, He does by His Spirit, “without the hand” of man (Job 34:20; Psa 104:30). Here He is represented using His power as Judge.
burning - (Mat 3:11, Mat 3:12). The same Holy Ghost, who sanctifies believers by the fire of affliction (Mal 3:2, Mal 3:3), dooms unbelievers to the fire of perdition (1Co 3:13-15).