So We desired that their Lord should give them in exchange one better than him in purity, as He did by giving them in [his] place the reassured soul which is better than him in purity and unblemishedness, and closer to mercy, to being loving and merciful since it [the reassured soul] is more affectionate towards the soul and the body and more beneficial to both and more compassionate towards them. It is possible that by 'parents' is meant that the grandfather and the father, and so they figuratively stand for the spirit and the heart, in which case his [the boy's] being 'closer to mercy', means that he is more suitable for them and more intensely affectionate [to them].