Muslims believe Abraham took Ishmael up on the mountain to sacrifice him. However, when the Koran talks about this scene, it leaves out the name of the son.

102. Then, when (the son) reached (the age of) (serious) work with him, he said: “O my son! I see in vision that I offer thee in sacrifice: Now see what is thy view!” (The son) said: “O my father! Do as thou art commanded: thou will find me, if Allah so wills one practising Patience and Constancy!” 103. So when they had both submitted their wills (to Allah., and he had laid him prostrate on his forehead (for sacrifice), 104. We called out to him “O Abraham! 105. “Thou hast already fulfilled the vision!” - thus indeed do We reward those who do right. 106. For this was obviously a trial- 107. And We ransomed him with a momentous sacrifice: 108. And We left (this blessing) for him among generations (to come) in later times: 109. “Peace and salutation to Abraham!” 110. Thus indeed do We reward those who do right. 111. For he was one of our believing Servants. 112. And We gave him the good news of Isaac - a prophet,- one of the Righteous. Surah 37:102-112

The Koran doesn’t say it was Isaac. It doesn’t say it wasn’t Isaac. The one with Abraham is only called “son.” However, by the end of Surah 37, verse 112, Muhammad mentions Isaac. Was this the son he was talking about all along in context?

The Bible is very clear who Abraham took to sacrifice on the mountain.

Some time later God tested Abraham. He said to him, “Abraham!”
“Here I am,” he replied.
Then God said, “Take your son, your only son, Isaac, whom you love, and go to the region of Moriah. Sacrifice him there as a burnt offering on one of the mountains I will tell you about.” Genesis 22:1-2

The Bible makes it clear that Isaac was the son who Abraham took the mountain as part of the promise given by God. The Koran does not contradict that statement since it does not say which son is on the mountain with Abraham.