Knowing The Word in Matthew 9:35-39

The Harvest Is Plentiful, the Laborers Few

35 And Jesus went throughout all the cities and villages, teaching in their synagogues and proclaiming the gospel of the kingdom and healing every disease and every affliction. 36 When he saw the crowds, he had compassion for them, because they were harassed and helpless, like sheep without a shepherd. [This is an OT metaphor. Where do we find it?] 37 Then he said to his disciples, “The harvest is plentiful [people are ready to respond to the gospel], but the laborers are few [men sent out to rescue others from judgment]; 38 therefore pray earnestly to the Lord of the harvest to send out laborers into his harvest.”