I think you are mistaken. The Old Testament Scriptures were written in Paleo-Hebrew, and Wikipedia says "Paleo-Hebrew script is an abjad of 22 consonantal letters", and that an abjad is "a writing system in which only consonants are represented, leaving the vowel sounds to be inferred by the reader. This contrasts with alphabets, which provide graphemes for both consonants and vowels". Wikipedia also says:
After the Talmud, various regional literary dialects of Medieval Hebrew evolved. The most important is Tiberian Hebrew or Masoretic Hebrew, a local dialect of Tiberias in Galilee that became the standard for vocalizing the Hebrew Bible and thus still influences all other regional dialects of Hebrew. This Tiberian Hebrew from the 7th to 10th century CE is sometimes called "Biblical Hebrew" because it is used to pronounce the Hebrew Bible; however, properly it should be distinguished from the historical Biblical Hebrew of the 6th century BCE, whose original pronunciation must be reconstructed. Tiberian Hebrew incorporates the scholarship of the Masoretes (from masoret meaning "tradition"), who added vowel points and grammar points to the Hebrew letters to preserve much earlier features of Hebrew, for use in chanting the Hebrew Bible. The Masoretes inherited a biblical text whose letters were considered too sacred to be altered, so their markings were in the form of pointing in and around the letters. The Syriac alphabet, precursor to the Arabic alphabet, also developed vowel pointing systems around this time. The Aleppo Codex, a Hebrew Bible with the Masoretic pointing, was written in the 10th century, likely in Tiberias, and survives into the present day. It is perhaps the most important Hebrew manuscript in existence.
So the Hebrew vowel points were not invented until at least the 7th century AD.
Concerning "jot and tittle", a jot is referring to the smallest Hebrew letter (y) and tittle is a very small part of a letter, like the dot of an 'i' in the English alphabet. Vincent's Word Studies says:
Jot is for jod, the smallest letter in the Hebrew alphabet. Tittle is the little bend or point which serves to distinguish certain Hebrew letters of similar appearance.
Barnes' Notes says:
One tittle - The word used here, in the Greek, means literally a little horn, then a point, an extremity. Several of the Hebrew letters were written with small points or apices, as in the Hebrew letter, shin (שׁ sh), or the Hebrew letter, sin (שׂ s), which serve to distinguish one letter from another. To change a small point of one letter, therefore, might vary the meaning of a word, and destroy the sense.
So Jesus was saying that the tiniest part of the law would not change. He was not talking about consonants and vowels. To quote a more modern translation, Matthew 5:18 (WEB):
(18) For most certainly, I tell you, until heaven and earth pass away, not even one smallest letter or one tiny pen stroke shall in any way pass away from the law, until all things are accomplished.
