By what he has entrusted to you, which is the prophethood. The 'ba' may relate to his saying, 'Call upon your Lord for us,' in two ways: one is that we seek your help in what we request from you of supplication for us, by the right of what you have from Allah's covenant and His honor in prophethood. Or, call upon Allah for us, seeking intercession through His covenant with you. Or it may be an oath that is answered, meaning: we swear by Allah's covenant with you that if You remove the torment from us, we will certainly believe in You until a time they reach, to a limit of time they will reach without a doubt, for they will be punished in it, and what has been given to them of delay and removal of punishment will not benefit them when they break their promise. This means: when We removed it from them, they suddenly broke their promise and hastened; they did not delay it, but as soon as it was removed from them, they broke their promise. So We took vengeance on them; We intended to take vengeance on them, so We drowned them. And to them: the sea that has no bottom. And it is said: it is the depths of the sea and most of its water, and its derivation is from tayammum, because those who benefit from it seek it. This is because they denied Our signs, meaning their drowning was due to their denial of the signs and their negligence towards them and their lack of reflection upon them.