COMMENTARY on 12:10
A. Yusuf Ali:

Translation:
Said one of them: "Slay not Joseph, but if you must do something, throw him down to the bottom of the well: he will be picked up by some caravan of travellers." 1641
Commentary:

1641  One of the brethren, perhaps less cruel by nature, or perhaps more worldlywise, said: "Why undertake the risk of blood-guiltiness? Throw him into the well you see there! Some travellers passing by will pick him up and remove him to a far country. If not, at least we shall not have killed him:" This was false casuistry, but such casuistry appeals to sinners of a certain kind of temperament. The well was apparently a dry well, deep enough to prevent his coming out, but with no water in which he could be drowned. It was Allah's Plan to save him alive, but not to make Joseph indebted to any of his brethren for his life!

 

Muhammad Asad:

Translation:
Another of them said: "Do not slay Joseph, but -rather - if you must do something - cast him into the dark depths of this well, [whence] some caravan may pick him up." 15
Commentary:
15  Sc., "and take him with them to a faraway land" (cf. the preceding verse). The term jubb - rendered by me as "well" - is usually applied to a desert well simply cut through the earth or through rock and not cased with stone: the implication being that this particular well did not contain enough water to drown Joseph, but was deep enough to hide him from sight.