Verse 141 opens with the statement: فَسَاهَمَ (fasahama: Then he participated in drawing lots...). These lots were drawn at a time when the boat was caught by a storm while in the middle of the waters. It was apprehended that its excessive weight might cause it to drown. It was decided that one person from the boat should be cast off into the waters. Lots were drawn to determine who would it be.
The Injunction of drawing lots
At this point, it should be borne in mind that the drawing of lots is a method of selecting somebody to do something through which one can neither prove someone's right, nor indict someone as a criminal. For example, no one can be proved to be a thief by drawing lots. Similarly, should two persons differ about the ownership of some property, it cannot be decided by drawing lots as to who owns it. However drawing of lots is permissible - rather, better - on an occasion where a person is totally entitled, Shari'ah-wise, to opt for any course out of the few permissible courses of action available. Now, it is up to him. He can, rather than go by his will and choice and select a course of action, arrive at a decisive line of action by drawing lots. For example, someone who has more than one wife and is going on a journey, then, he has the right to take the wife he elects to take with him. Now, rather than do this following his will and choice, if he were to draw lots, it would be better - so that no one is disheartened. The Holy Prophet t used to do that.
The purpose behind the drawing of lots in this event relating to Sayyidna Yunus (علیہ السلام) was not to label anyone as some culprit. In fact, to save a whole boat-full of passengers, anyone could have been cast away into the waters. So, the name of the person to be cast was determined by drawing lots.
Immediately next in the verse, it was said: فَكَانَ مِنَ الْمُدْحَضِينَ and was the one who was defeated." The word: اِدحَاضُ (idhad) literally means to defeat someone or to make him fail, lose. The sense is that it was his name that came up in the draw - and he threw himself into the waters. No one should raise the objection that it was some sort of a suicide plunge, for it is possible that the shore was near and he intended to swim ashore.