Why could Jesus not pour out grace to Gentiles during His earthly ministry?
During His earthly ministry, Jesus was under the sovereign agreement with Israel and Abraham, so He could not pour out grace to Gentiles until Israel had every opportunity to hear the offer of the King and Kingdom. After Israel rejected it, God would turn to the Gentile world.
Les explains that Israel was the privileged people who had the Word of God and could feast at that table. Jesus' illustration of not taking the children's bread and casting it to the dogs showed He could heal a Gentile if He wanted to, but He was operating under the sovereign agreement with Israel and Abraham and the covenant promises. That agreement meant He could not pour out grace to Gentiles until Israel had every opportunity to hear the offer of the King and the Kingdom. When Israel rejected it, God then turned to the Gentile world.