Leap of Faith

The Leap of Faith was an acrobatic move in which the person performing it dived from atop a high structure to land, unharmed, in a conveniently placed pile of hay or other soft landing material.

The Leap of Faith was integral for the members of the Assassin Order, and served as a requirement for their initiation.

Description
The acrobatic move itself consisted of a vertical leap, with a completely straight back, followed by a body-roll in mid-air to allow the one performing it to land on his or her back.

The move could also be performed by simply walking off a ledge, moving the entire body forward. This method was used by the Roman Assassin recruits after their initiation ceremony.

Leaps of Faith could be performed by Free Running off any high ledge or beam. Areas from which a Leap could be performed were often marked by bird droppings with small hay patches, and pigeons perched upon the ledge. Leaps of faith could also be performed while hanging on a ledge or climbing near a bale of hay.

High Middle Ages
The Leap of Faith was used to descend from View Points, each of which always provided a suitable safe target for it. However, it could be used to jump down from anywhere, if, of course, there was a safe target below.

It was also handy in losing pursuing guards on rooftops, as leaping down to street level automatically caused the Assassin to leave the pursuers' line of sight.

Renaissance
Though Altaïr only performed Leaps of Faith into piles of hay, Ezio Auditore could make use of water and other piles of soft material, such as piles of leaves or flower petals.

Upon traveling to Rome, Ezio made use of the Leap of Faith to quickly escape the Borgia Towers he climbed and set aflame.

As per tradition, whenever Assassin recruits were initiated, Ezio also required them to perform a Leap of Faith from the top of the Tiber Island hideout, into the Tiber River below.

Modern times
In 2000, Daniel Cross performed a Leap of Faith into the Arabian Sea, in order to escape the Assassins' Dubai headquarters upon murdering The Mentor with his newly acquired Hidden Blade.

Desmond Miles performed his first Leap of Faith in the run-down, modern Monteriggioni in 2012, after witnessing (due to the bleeding effect) Ezio climbing up to a View Point.

Additionally, at Abstergo Industries, several Abstergo recruits also performed Leaps of Faith through the simulations they participated in, within the Animus training program.

Trivia
Assassin's Creed

Assassin's Creed II Other
 * Near the beginning of the game, when Masyaf is attacked by Templars, three Assassins display their devotion by performing Leaps of Faith from a cliff. This is based on a historical incident involving the Hashshashin, in which their leader proclaimed that his followers were more devout than any, and would follow all commands he gave. As shown in the game, he ordered several men to jump from a cliff "to their deaths," which they did. The incident is also depicted in the novel Alamut, by Vladimir Bartol; though only one man leaps from a tower, while another kills himself with a dagger.
 * There is actually nothing coincidental about the placement of the piles of hay. It is explained that the bales of hay and the birds that denote the location of a View Point have been programmed into the memory by Lucy Stillman, as a way to help out in the navigation of the memory.
 * When being pursued by Ezio, Francesco de' Pazzi leaps off the Palazzo della Signoria into a haystack for a quick escape. This was the only known example for a non-Assassin committing a form of a Leap of Faith until Assassin's Creed: Brotherhood.
 * To achieve the "High Dive" achievement, you must perform a Leap of Faith from Giotto's Campanile in Florence, as it is the highest viewpoint in the game.
 * Ezio can perform an alternative Leap of Faith by hanging from a ledge or View Point and falling backwards onto a safe spot, as long as he is high enough, and the safe spot is directly below him. Ezio is forced to do this at least once, after speaking with his father during the "Jailbird" memory.
 * In reality, it is unlikely that a haystack in a cart would be able to safely cushion someone falling from a great height. The momentum may either cause the cart to collapse or the person jumping to fall through the bottom. Hay is also sharp, therefore falling into it at such a speed would surely cause injury.
 * It is suggested that very few of the modern-age Assassins perform the Leap of Faith, due to Lucy Stillman saying it was "pretty awesome" when she witnesses Desmond Miles performing his first-ever Leap from the walls of Monteriggioni. It should be noted that Lucy does not perform the Leap herself, and instead takes a ladder down the cliff to follow Desmond.
 * In Assassins Creed II: Discovery, Ezio can also perform the alternative Leap of Faith by hanging above a haystack and letting go of the ledge. Doing so correctly will let Ezio flip three times.
 * Also in Discovery, Ezio can perform a Leap of Faith into a bush.
 * In Assassin's Creed: The Secret Crusade, it is mentioned that the haystacks used in the Leaps of Faith at the Templar siege of Masyaf were placed there on the orders of Rauf.
 * As an easter egg in Metal Gear Solid: Peace Walker, Big Boss (and the soldiers he has recruited) can perform Leaps of Faith into a straw box called the "Assassin Straw Box."
 * An easter egg in The Witcher 2: Assassins of Kings shows an individual dressed in Assassin clothing dead on top of a collapsed hay cart; the main character comments "Guess they'll never learn."