Prayer and Old Testament Israel
I ran across this statement a while ago: "The effectual fervent prayer of a righteous man availeth much! However, I think we can't look at promises made to Old Testament Israel, and expect God to keep them to 2016 America.....". I believe this person was referring to the covenants made between God and his people, Israel. Could you comment on this and enlighten me?
Within the Sinaitic covenant (Exodus 19:3-6), God did make promises to Old Testament Israel that had application limited to them. In addition, God gave Old Testament Israel ceremonial and civil laws that are no longer applicable today.
On the other hand, there are many promises God that made to Old Testament Israel that are still applicable to 2016 America. Chief among them are the promises of a Messiah, Jesus Christ, who came into the world as a child in Bethlehem and who will return in glory on the last day to judge all people.
When James wrote that “The prayer of a righteous person is powerful and effective” (James 5:16), he was not referencing any promises or covenants that God had made with Old Testament Israel. While James goes on in the next verse (v. 17) to provide an example of powerful and effective prayer in the person of Elijah, an Old Testament prophet, the context of James 5 does not limit powerful and effective prayer to Old Testament followers of the Lord.
Knowing the context of the quote in your question would probably help us understand the point the person was trying to make. As it stands, your quote lists a statement of fact—that prayer is powerful and effective—and a statement about promises made to Old Testament Israel and their applicability to Christians today. By themselves, the two statements are not accurately connected.