salaam all,
My understanding is as follows:
37:102 When he grew enough to work with him, he said, "My son, I am seeing in a dream that I am sacrificing you (i.e. giving you up) for a noble cause. What do you think?" He said, "O my father, do what you are commanded to do. You will find me, God willing, patient.
37:103 So when they both submitted (or became peaceful), and he (Abraham) brought him to his forehead.*
37:104 And We called to him: "O Abraham,
37:105 You have fulfilled the vision." It is such that We reward the doers of good.
37:106 Surely, this was a clear test.
37:107 We exchanged him with a tremendous sacrifice.
37:108 And we left for him among the later generations.
*Root: Ta-Lam-Lam: lay one down upon one's kin (neck/cheek/breast), or forehead in this case. This could be commonly done when one says goodbye to a loved one such as a son/daughter/etc.
Note how it says he "fulfilled the vision".
Giving up one's son for a noble cause (e.g. spreading the message) is indeed an exacting test, and a tremendous sacrifice.
Note how in the story of Abraham, as per Quran, he is not mentioned being with his two sons at the same time, and that Ishmael is never mentioned being with Isaac at the same place, implying a separation. Abraham is also never mentioned with Isaac in the latter half of the story in Quran. This provides a perfect fit with the above theory.