Tafsir of Yusuf 12:14

(They said, "If the wolf should eat him while we are a 'usbah")—meaning, while we are a group worthy of having matters bound up with us, and capable through our opinions and management of handling misfortunes. The lam prefixed to the conditional particle is there to introduce an oath.

His statement—Exalted is He—( "Indeed, we would then be khasirun [losers]") is a response that functions in place of the (actual) consequence of the conditional.

Khasar (loss) here means either:

1. Destruction.
2. Acknowledgment of weakness, or being deserving of it.
3. Being deserving of a supplication against us—meaning: we are weak, incapable, or deserving of destruction because we possess no utility, and there is no benefit in our lives. Or, we are deserving that one should pray for our loss and ruin, such that it is said: "May Allah destroy them and ruin them, for their brother was eaten by a wolf while they were with him."

It is also possible that it carries its literal meaning: if we are unable to protect him—the most precious thing to us—then our livestock are surely lost and we have suffered the loss of them.

They limited themselves to addressing their father’s fear of the wolf, despite the fact that he mentioned two reasons for not wanting Joseph to leave: his sadness at his separation, and his fear of the wolf. They did this because the wolf was the stronger argument for refusal, whereas the sadness was temporary, based on the assumption that they would return quickly. Alternatively, it may be because his sadness was merely a manifestation of his fear for him, so negating the second implies negating the first. Or, perhaps they avoided the topic of his sadness because it was the very reason for their envy of him, and thus they turned a deaf ear to it.