There was Asaf on Al-Safa and on Al-Marwah Nailah, so the one running between Al-Safa and Al-Marwah should not ignore it. When he ascends Al-Safa, his name is considered a sign of regret, which is his sadness over what he missed of wasting the rights of God Almighty upon him. This is why he greets the House with supplication and remembrance to remind him of that, and sadness appears on him when he reaches Al-Marwah. It is a position of Na'ila that he takes from the Nile, which is the gift, so he obtains Na'ila's regret, i.e. his reward, and he does that in the seven rounds because God has been grateful to him with seven attributes so that he can dispose of them and spend them in fulfilling the rights of God. He does not waste any of them and he regrets that, so God gives him his reward in considering Na'ila with marwa until he finishes.