The King James edition of the Bible, 'an Hebrew'

The King James Bible uses 'an' before h— whether or not the 'h' was silent.

For example, the King James Bible has:

An horse is a vain thing for safety: neither shall he deliver any by his great strength.

And Jacob journeyed to Succoth, and built him an house, and made booths for his cattle: therefore the name of the place is called Succoth.

However, it appears that the 'h' in Hebrew was indeed silent back then. The word Hebrew came from Old French Ebreu, and the 'h' was added, like the 'b' in debt, so the spelling would better correspond with the original Latin.

By looking at Shakespeare, who usually uses an only before silent 'h', you can discover that there were a few words where the 'h' was silent back them but isn't now, like humble, host and, in the U.K., herb. And Shakespeare has:

If thou wilt, go with me to the alehouse; if not, thou art an Hebrew, a Jew, and not worth the name of a Christian.

Even though he usually uses 'a' before horse and house:

A horse! a horse! my kingdom for a horse!

For Venus smiles not in a house of tears.