I read in my Bible that Sarah was the first wife of Abraham but had delay in conception. Sensing that she might not be able to get pregnant again, she advised her husband (Abraham) to impregnate their maid Hagar,she got pregnant, bore a son and named him Ishmael.
Later she became too proud and refused to give regards to her mistress(Sarah), then she was sent packing for insubordination, though the Angel of the Lord instructed her to go back and be submissive,we were not told how it went down ...

Genesis 16:1 Now Sarai Abram's wife bare him no children: and she had an handmaid, an Egyptian, whose name was Hagar.
16:2 And Sarai said unto Abram, Behold now, the LORD hath restrained me from bearing: I pray thee, go in unto my maid; it may be that I may obtain children by her. And Abram hearkened to the voice of Sarai. 16:3 And Sarai Abram's wife took Hagar her maid the Egyptian, after Abram had dwelt ten years in the land of Canaan, and gave her to her husband Abram to be his wife. 16:4 And he went in unto Hagar, and she conceived: and when she saw that she had conceived, her mistress was despised in her eyes.
16:5 And Sarai said unto Abram, My wrong be upon thee: I have given my maid into thy bosom; and when she saw that she had conceived, I was despised in her eyes: the LORD judge between me and thee.
16:6 But Abram said unto Sarai, Behold, thy maid is in thy hand; do to her as it pleaseth thee. And when Sarai dealt hardly with her, she fled from her face.
16:11 And the angel of the LORD said unto her, Behold, thou art with child, and shalt bear a son, and shalt call his name Ishmael; because the LORD hath heard thy affliction.

Later, Sarah became pregnant at about 90yrs and bore Isaac -which God said would be a child of promise. I also read that Isaac was actually the one God called "the only child" of Abraham and asked him to sacrifice Isaac unto Him and not Ishmael ...

Genesis 21:1 And the LORD visited Sarah as he had said, and the LORD did unto Sarah as he had spoken.
21:2 For Sarah conceived, and bare Abraham a son in his old age, at the set time of which God had spoken to him.
21:3 And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac. 21:8 And the child grew, and was weaned: and Abraham made a great feast the same day that Isaac was weaned.
21:10 Wherefore she said unto Abraham, Cast out this bondwoman and her son: for the son of this bondwoman shall not be heir with my son, even with Isaac.
Genesis 22:1 And it came to pass after these things, that God did tempt Abraham, and said unto him, Abraham: and he said, Behold, here I am.
22:2 And he said, Take now thy son, thine only son Isaac, whom thou lovest, and get thee into the land of Moriah; and offer him there for a burnt offering upon one of the mountains which I will tell thee of Genesis 22:3 And Abraham rose up early in the morning, and saddled his ass, and took two of his young men with him, and Isaac his son, and clave the wood for the burnt offering, and rose up, and went unto the place of which God had told him. 22:4 Then on the third day Abraham lifted up his eyes, and saw the place afar off. 22:5 And Abraham said unto his young men, Abide ye here with the ass; and I and the lad will go yonder and worship, and come again to you. 22:6 And Abraham took the wood of the burnt offering, and laid it upon Isaac his son; and he took the fire in his hand, and a knife; and they went both of them together. 22:7 And Isaac spake unto Abraham his father, and said, My father: and he said, Here am I, my son. And he said, Behold the fire and the wood: but where is the lamb for a burnt offering? 22:8 And Abraham said, My son, God will provide himself a lamb for a burnt offering: so they went both of them together. 22:9 And they came to the place which God had told him of; and Abraham built an altar there, and laid the wood in order, and bound Isaac his son, and laid him on the altar upon the wood.
22:10 And Abraham stretched forth his hand, and took the knife to slay his son.
22:11 And the angel of the LORD called unto him out of heaven, and said, Abraham, Abraham: and he said, Here am I.
22:12 And he said, Lay not thine hand upon the lad, neither do thou any thing unto him: for now I know that thou fearest God, seeing thou hast not withheld thy son, thine only son from me.
22:13 And Abraham lifted up his eyes, and looked, and behold behind him a ram caught in a thicket by his horns: and Abraham went and took the ram, and offered him up for a burnt offering in the stead of his son. .

The unnecessary confusion now is,Christians believe that it was Isaac that was to be used as sacrifice but was replaced with ram, then Jesus came to cancel the killing of rams by standing as the, in this case, Lamb of God.
But the Moslems believe it was Ishmael.
Why this confusion?
It ILEYA is truly to be celebrated, which religion is it to do it.
i think it was this mistake of Abraham, caused by a woman again! ,that is still causing religion upheavals today. Even the enslavement in the land of Egypt was a payback time for the seeds of Isaac for what Sarah nd Abraham caused Hagar nd Ishmael to pass through, and also for Abraham impatience and unbelief.
A lesson for us all.

I'm as confused as the OP in this issue . I want to believe that Islam came to exixstence through Ishmael. because if you read futher,God said He will establish a kingdom through Ishmael. Also, the Bible said he will be 'WILD'. May be that is why Islam dominated countries all over the world love violence.

Godfullsam: I'm as confused as the OP in this issue . I want to believe that Islam came to exixstence through Ishmael. because if you read further,God said He will establish a kingdom through Ishmael. Also, the Bible said he will be 'WILD'. May be that is why Islam dominated countries all over the world love violence.

of course, Islam came from Ishmael as Christianity came from Isaac...