Tethering was introduced in iPhone OS 3.0 but iPhone OS 3.1 disabled the tethering trick. The only way to get tethering on the iPhone is either jailbreaking or waiting for an official update from Mobily.
We will post more info as soon as the tethering update is released.
Arabic version of this post on SaudiMac.net.
The Mac Observer has linked to this post.