1. Q. “There are no vowels in the Hebrew letters of the sacred Name YHWH, so how can we know how to pronounce it correctly?”
Answer (1). If the Hebrew cannot be properly deciphered because of lack of vowels, then our entire Old Testament translation – originally written in a Hebrew script without vowels – is unreliable!
Remarkably, of the 22 letters of the Hebrew alphabet, Yahweh preserved His Name with three of the four letters that in the Hebrew ARE used as vowels as well as consonants: yothe (y), hay (h), and waw (w). (The aleph, a, is also used as a vowel.) This fact can be verified in nearly any Hebrew grammar, including: A Beginner’s Handbook to Biblical Hebrew(Horowitz), p. 7 under “Vowel Letters”; The Berlitz Self-Teacher, p. 73 under “The Vanishing Dots”; Hebrew Primer and Grammar (Fagnani and Davidson) p. 10 under “The Quiescents and Mappiq,” and How the Hebrew Language Grew(Horowitz), p. 28. In addition, about the seventh century, Jewish scribes known as Masoretes preserved the pronunciation of the Hebrew with diacritical marks or vowel points added to Hebrew words (Eerdman’s Bible Dictionary, p. 699).
Three of these vowel-letters form the Tetragrammaton or Yahweh’s Name, why (the hay is repeated). But we need not rely solely on modern scholarship for this information. We can take the word of an eyewitness! The first century Jewish general, priest, and historian Flavius Josephus (37-100?) writes about the sacred Name engraved on the headpiece of the high priest: “A mitre also of fine linen encompassed his head, which was tied by a blue riband, about which there was another golden crown, in which was engraven the sacred name [of Yahweh:] it consists of FOUR VOWELS” (Wars of the Jews, Book 5, chapter 5, p. 556).