“For truly, I say to you, until heaven and earth pass away, not an iota, not a dot, will pass from the Law until all is accomplished.” (Matthew 5:18, ESV)
The “iota” is the English transliteration of the Greek word ιωτα. The iota is the ninth (9th) letter of the Greek alphabet. The iota is the nearest equivalent of the Hebrew yod, which is the tenth (10th) letter of the Hebrew alphabet.
The iota is the smallest projection of any part of a letter such as an accent or breathing mark of a text. The meaning of Matthew 5:18 is “not the smallest part of a letter will be abolished in the law or the prophets until all things are accomplished or fulfilled.”
Jesus Himself is affirming the absolute inerrancy and authority of the Old Testament as the very word of God. He affirms the inerrancy and authority of the Old Testament right down to the smallest stroke or letter of the alphabet. The significance of this to you and me is the reasoning that the New Testament did not supplant or abrogate the Old Testament. The New Testament has fulfilled and exonerated the Old Testament. The ceremonial aspects of the Mosaic law were fulfilled in Jesus Christ. So the smallest letter will not be erased or destroyed. All is fulfilled in Christ. Not in you or anything that you can do; not in "the church" since no church can save.
This means everything thing written in the Scriptures will be fulfilled. This includes all of the promises of blessing and bliss. This includes all of the judgment and punishment. Not one promise as small as the smallest letter or breathing stroke in the Old Testament or New Testament will go unfulfilled. Do not kid yourself and think that the majestic, holy, righteous, and glorious God will overlook one statement of truth in His Word for anyone.