What did the letter H represent in the names Abraham and Sarah?
The added letter H in Abraham and Sarah represented Yahweh, or Jehovah. When God brought Abram and Sarai to the covenant promises, He changed their names, and that H carried the divine connotation, marking the covenant relationship and blessing attached to their new names.
Les explains that just as the number 5 was associated with grace, the letter H was associated with Yahweh or Jehovah. When God brings Abram and Sarai to the place of the covenant promises, He changes their names to Abraham and Sarah, and the H is included in both. God tells Abraham that Sarai's name will be changed to Sarah, again with that H connotation. This comes with promises that He will bless her, give Abraham a son by her, and make her a mother of nations, with kings of people coming from her.
And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be.