Why do Catholics “hail Mary” when the religion clearly forbids it? Are they reading a different Bible?

Throughout the Middle Ages — until around 1500 in fact — the Hail Mary simply consisted of two short passages from scripture, with the addition of the two names “Mary” and “Jesus”:

Hail [Mary], full of grace. the Lord is with you. (Luke 1:28) — the name “Mary” was added because it was clearly implied by the context, but needed to be stated explicitly when the verse is quoted on its own.

Blessed are you among women, and blessed is the fruit of your womb [Jesus]. (Luke 1:42) —

The name “Jesus” was added because it also was implied by the context, similar to the introduction of the name “Mary”.

This form of the Hail Mary was used in England up until the reign of Henry VIII. In Germany it even remained in use among the Lutherans (the original Protestants!). They did not see the Hail Mary as contrary to the Bible. The first Protestants (e.g. Luther and Calvin) were more respectful of Mary than many modern Protestants who ignore her almost completely.

A footnote to an English translation of the Medieval Sarum missal notes:

The full form in 1526 would be "Hail, Mary, thou that art highly favoured, the Lord is with thee. Blessed art thou among women and blessed is the fruit of thy womb, Jesus," with possibly the addition, dated by Gavantus in 1508, "Holy Mary, mother of God, pray for us sinners," and the Franciscan addition of 1525, " Now and in the hour of our death," Thesaur. Sacr. Rit., edit. 1738, Tom. ii., part i, p. 235.

So the Hail Mary was extended twice in the 16th century, but dropped by Anglican and Calvinist churches as part of their reformations. However the medieval version continued in use among some Protestants, notably Lutherans.

And so you are overreaching in your claim that the Bible “clearly forbids” the Hail Mary. In fact, the Bible clearly contains almost the entire pre-1500 version of the Hail Mary verbatim, and clearly implies the two additional words “Mary” and “Jesus”.

The 16th century additions may be defended on theological grounds, just as they may also be disputed on theological grounds. But it is overreach to claim that the scriptures “clearly” teach one side of that debate. Both sides require inferences from various biblical statements to build their case. Of course, the Catholic side of the debate does not accept the Calvinist claim that only things explicitly taught in scripture should be allowed because (among other things) that principle is not itself explicitly taught in scripture — it is a self-contradictory and therefore self-defeating principle.

What the scriptures do clearly teach is that we should accept other Christians who are seeking to glorify God, regardless of whether we have the same practices as they have (Romans 14). Focusing on Mary focuses attention on the incarnate God: Jesus, the child Mary bore and raised. She is blessed because of Him. It is this very humanness of God, of Christ, that the Hail Mary emphasises — and the fact that she was the woman God chose to be the mother of His Son, and of whom the scriptures say “all generations shall call me blessed”. The Hail Mary actually fulfils that scripture as each generation in turn acknowledges her as blessed.

So the objection to the Hail Mary comes from reading and interpreting the Bible differently to Catholics, rather than the Bible explicitly forbidding the Hail Mary. Overreach happens when we insist that the Bible is “clearly” on our side in a matter of contention among Christians. Such contentions exist precisely because the Bible is not as clear and simple as we may want to believe. And we can even gain from listening to the “other side” rather than simply dismissing it.