These wealthy individuals were landowners who exploited their workers (5:1). They are like those in 2:6 who oppressed and took Christians to court. These rich people exploited the day laborers who harvested their fields.
cries … have reached the ears of the Lord: God hears the prayers of the oppressed (see Deuteronomy 24:14–15). Even while the laborers are still suffering, the Lord has heard them (see Exodus 3:7).
the Lord of Hosts (1 Samuel 17:45; Psalm 103:20–21; Romans 9:29): This title emphasizes God’s power to act when the oppressed cannot.