"Except those upon whom Allah has mercy." Al-Hasan said: Meaning, from among the believers, some of them shall intercede for others, and that shall benefit them before Allah.
﴿إِلَّا من رحم الله﴾ قَالَ الْحسن: يَعْنِي: من الْمُؤمنِينَ يشفع بعضُهم لبَعض؛ فينفعهم ذَلِك عِنْد الله.