Isaiah 56 begins with an exhortation concerning justice. In parallel phrases, Yahweh instructs Israel to “guard judgment” ( mishpat ) and to “do justice” ( zedaqah ). Along with God’s statutes and commandments, His judgments are to by guarded (Leviticus 18:5, 28; 25:18). “Guarding” judgment suggests a conservative, protective, preserving something already achieved; “doing” justice is more active, accomplishing something not yet achieved. The two go together: Unless Yahweh’s judgments are guarded and preserved, justice will not be done.
The reason for the exhortation is that God is coming. A parousia is on the horizon. Those who have guarded judgment and acted with justice are prepared for the coming of salvation. Isaiah 56:1 anticipates the message of John the Baptist: Repent for the kingdom of God is at hand.
When the apocalypse of justice comes, only those who have guarded judgment and practiced justice will stand. Only they will be delivered.