Those who think that Hagar was not Abraham's wife, here is the answer:

Genesis 16:3Then Sarai, Abram�s wife, took Hagar her maid, the Egyptian, and gave her to her husband Abram to be his wife, after Abram had dwelt ten years in the land of Canaan.

That clearly shows that Hagar was Abraham's wife and who would expect a great prophet to have a child out of wedlock, a great sin. Now we need to see who was born first and who bore it regrdless where on earth they lived.

Genesis 16:16 Abraham was eighty-six years old when Hagar bore Ishmael to Abraham.

Genesis 21:5 Now Abraham was one hundred years old when his son Isaac was born to him.

Let us stop here and do some simple maths, 100-86=14 that is the age of Ishmael when Isaac was born.

Genesis 22:5 Abraham said to his young (his helpers that went with him) men, �Stay here with the donkey; the lad and I will go yonder and worship, and we will come back to you.�

Now remember here the word "lad" for Abraham's son, who was a young boy then.

So far we see that Ishmael is the first son, and if any say to him take your only son, it will 100% mean Ishmael only before the birth of Isaac.

Now something is wrong with this verse:

Genesis 22:2 Then He (God)said, �Take now your son, your only son Isaac, whom you love, and go to the land of Moriah, and offer him there as a burnt offering on one of the mountains of which I shall tell you.�

In my opinion someone did not fix it right. Because by the time Abraham had Isaac, he already had Ishmael. So Isaac cannot be refered as "the only son"