Actually, as was pointed out here earlier, it as given to Abraham and his descendents. Ishmael was one of them.
No, it most certainly was NOT given to Ishmael's line, as has also been pointed out quite clearly in this thread. The Bible is crystal clear that the land was given to the Abraham/Isaac/Jacob line, NOT to Ishmael. Read post 54. Sim does an excellent job of summarizing the issue as presented by the Bible.
You're relying on a single verse out of context, in which it says Abraham and his descendants. What's key to understand in that one verse is that it does NOT say it is given to Abraham and ALL his descendants. It simply says "descendants." Then, as you continue to read what else God has to say on the issue, it is brilliantly clear which descendants it was given to.
MM