"For all the land which thou seest, to thee will I give it, and to thy seed for ever."
They construe this verse to teach that a large chunk of the Middle East still belongs to the Jews today, including the ancient lands of Edom and Moab, even though God said in Deuteronomy 2:5, 9 that He would never give those lands to the Jews.
Christian Zionists regard God's covenant with Abraham, including the land grant, as an unconditional covenant. They admit that the Jews have broken that covenant, and have rejected their Messiah, but insist that Palestine still belongs to the Jews because God gave it to them "forever." However, the Bible teaches that God's covenant with Abraham and his descendants were a conditional covenant, not unconditional.
In Genesis 17:9-14 the Jews were warned that they must keep the covenant or be cut off from God's people. Leviticus 26:40-45 teaches that the Jews must confess and forsake their sins in order to maintain the covenant. Joshua 23:15-16 and 2 Chronicles 7:19-22 not only teach that the covenant was conditional, but they also specify that the Jews would lose their land grant if they broke the covenant.
In Exodus 12:23-24, God ordained the ordinance of the Passover to be observed "forever."
In Deuteronomy 18:3-5 the Levites are ordained to be God's ministers, and to receive the offerings of the people, "forever."
Leviticus 16:29 specify that the Day of Atonement is to be observed "forever."
The same reasoning applies to the land grant of Palestine to the Jews. The covenant and the land promise to the Jews were not eternal, to last until the end of time. The Jews did not keep the conditions of the covenant, and for this reason God took away the kingdom of God from them, Matthew 21:42-45, and gave it to the New Israel (Galatians 6:16,) the Church which consists of believing Jews and Gentiles.
The inheritance of the new Spiritual Israel is not land in the Middle East, but rather the New Jerusalem in heaven. The old Jerusalem on earth is of absolutely no importance to God's people, John 4:21, Galatians 4:24-28, Hebrews 12:18-24. The final disappearance of the old covenant took place in 70 AD when the Romans destroyed the Temple, the City of Jerusalem, and the Jewish state. There is no statement or hint in the New Testament that God will revive the Jewish state. Nowadays there are prominent evangelists who preach to their followers that God never fulfilled His promise of giving all the land of Palestine to the Jews.
They support whatever action necessary, even nuclear war, to obtain Arab lands in the Middle East and give them to the Jews. Read Joshua 11:23, Joshua 21:43-45, 2 Samuel 8:3, 1 Kings 4:21, 1 Kings 8:56, 2 Chronicles 9:26 and Nehemiah 9:7-8, 24 and it will become very clear that God did give all of the land promised to the Jews. The prophet Jeremiah is often quoted to prove that God promised a restoration of the Jews to their land and that the promise began to be fulfilled in 1948 AD. Instead of rejoicing in the New Covenant which was promised to all God's people, Jeremiah 31:31-34, they want to go back to the Old Covenant which has been forever abrogated.
The duty of Christian churches today is to seek the well-being of Jews according to the flesh, Romans 9:3. We will accomplish that, not by lobbying for the territorial expansion of Israel, but rather by preaching the Gospel and planting churches, thereby giving all Jews and Gentiles an opportunity to enter the heavenly Jerusalem for all eternity.