The field is the world.
It is important to remember that, in accord with the plan of God, Jesus Christ came primarily to seek the lost sheep of the house of Israel. He was their Messiah, their Kinsman-Redeemer (Leviticus 25:48). While His heart went out to all mankind, His special message was to them first. Upon their rejection of allegiance to His authority (John 19:15), He commanded His disciples to carry His gospel to all men everywhere (Matthew 28:19–20).
But while His earthly testimony was to Israel, His heart was concerned about all. It was because “God so loved the world” that He sent His only begotten Son into this scene (John 3:16); therefore we need not be surprised to see His grace leaping over national boundaries and going out even to sinners of the Gentiles, who were “strangers from the covenants of promise,” who were without God and, so far as any knowledge of His Word was concerned, were without hope in the world (Ephesians 2:12). Grace recognizes no national or racial barriers, but sees in all men of all nations sinners for whom Christ died and who may be transformed into saints by the mighty life-giving power of the Holy Spirit.
Have ye carried the living water
To the parched and weary soul?
Have ye said to the sick and wounded,
“Christ Jesus makes thee whole?”
Have ye told My fainting children
Of the strength of the Father’s hand?
Have ye guided the tottering footsteps
To the shore of the “golden land?”
H. A. Ironside, The Continual Burnt Offering: Daily Meditations on the Word of God (Neptune, NJ: Loizeaux Brothers, 1994), 163.