Allah says that when Yusuf's brothers took him from his father, after they requested him to permit that,
(they all agreed to throw him down to the bottom of the well,) This part of the Ayah magnifies their crime, in that it mentions that they all agreed to throw him to the bottom of the well. This was their intent, yet when they took him from his father, they pretended otherwise, so that his father sends him with a good heart and feeling at ease and comfortable with his decision. It was reported that Ya`qub, peace be upon him, embraced Yusuf, kissed him and supplicated to Allah for him when he sent him with his brothers. As-Suddi said that the time spent between pretending to be well-wishers and harming Yusuf was no longer than their straying far from their father's eyes. They then started abusing Yusuf verbally, by cursing, and harming him by beating. When they reached the well that they agreed to throw him in, they tied him with rope and lowered him down. When Yusuf would beg one of them, he would smack and curse him. When he tried to hold to the sides of the well, they struck his hand and then cut the rope when he was only half the distance from the bottom of the well. He fell into the water and was submerged. However, he was able to ascend a stone that was in the well and stood on it. Allah said next,
(and We revealed to him: "Indeed, you shall (one day) inform them of this their affair, when they know (you) not. ") In this Ayah, Allah mentions His mercy and compassion and His compensation and relief that He sends in times of distress. Allah revealed to Yusuf, during that distressful time, in order to comfort his heart and strengthen his resolve, `Do not be saddened by what you have suffered. Surely, you will have a way out of this distress and a good end, for Allah will aid you against them, elevate your rank and raise your grade. Later on, you will remind them of what they did to you,' i
(when they know not.) "Ibn `Abbas commented on this Ayah, "You will remind them of this evil action against you, while they are unaware of your identity and unable to recognize you."