Evil is that for which they have sold their souls-- that they should deny what Allah has revealed, out of envy that Allah should send down of His grace on whomsoever of His servants He pleases; so they have made themselves deserving of wrath upon wrath, and there is a disgraceful punishment for the unbelievers.

And the two seas are not alike: the one sweet, that subdues thirst by its excessive sweetness, pleasant to drink; and the other salt, that burns by its saltness; yet from each of them you eat fresh flesh and bring forth ornaments which you wear; and you see the ships cleave through it that you may seek of His bounty and that you may be grateful.