Harvest refers to the great number of people who are ready to hear and respond to God’s message (see also Matthew 13:24–30, 36–43; Mark 4:26–29; John 4:35–38; Revelation 14:15–20).
the Lord of the harvest: God is the true master of the harvest. All ministries are under his call (see Matthew 23:8–10, 13). So Jesus encourages his disciples to pray for God to send out more workers.