Genesis 37:20
Come now therefore, and let us slay him, and cast him into some pit, and we will say, Some evil beast hath devoured him: and we shall see what will become of his dreams. Come now therefore, and let us slay him, and cast him into some pit, and we will say, Some evil beast hath devoured him: and we shall see what will become of his dreams.
Jacob loved Joseph more than his other children, and that partiality and indulgence helped in part to provoke his brothers' hostility toward him. That envy and hatred grew until it became murderous intent, with envy joined by cruelty, contempt, and desire for revenge overcoming them. The verse records their proposal to kill Joseph because of his dreams, to cast his body into a pit to hide it, and to deceive their father by saying a wild beast had devoured him.
Their question about what would become of his dreams was mocking contempt for dreams they resented, expecting them to come to nothing. It also expressed a deliberate purpose to thwart the resented future, to stop the dreams from coming true, to prevent Joseph from becoming greater than themselves, to be troubled by his dreams no more, and to make fulfillment impossible. Reuben opposed the murder, warning that it would bring guilt and God's curse, and proposed putting Joseph alive into a pit so he could later rescue him and return him to his father, which prevented outright killing at that time.
The plot still led to Joseph being thrown into a pit and separated from home, but Judah then persuaded the brothers to sell him as a slave instead, and God saw Joseph's distress. Joseph's suffering appeared to defeat the purposes revealed in his dreams, but God overruled the very course meant to prevent his rise to bring about his dominion over his brothers, making him a savior to his father's family and giving him signal victories despite persecution for doing right. The experience also exposed faults in Joseph fostered by that upbringing, including self-sufficiency and demandingness, which hardship would correct.
The plan foreshadows how Christ's enemies sought to prevent his authority and kingship by having him killed, for the chief priests and elders were jealous lest he draw the people away and become higher in authority and king of the Jews, so they agreed to take him privately with false witnesses and put him to death while crying for crucifixion, thinking to prevent his becoming king. Yet by murdering him they brought about his becoming Redeemer of mankind, Savior of the fallen race, and ruler over the whole world. God's use of such crimes for his own glory and the good of man did not lessen the guilt of those who committed them, which remained just as heinous as though his providential hand had not controlled events.