Silsilat al-Ahadith al-Sahihah

Mus'ab bin Sa'd narrates from his father, Sayyiduna Sa'd (may Allah be pleased with him), who said: I asked the Messenger of Allah (peace and blessings be upon him), "Which people are tested the most severely?" He (peace and blessings be upon him) replied: "The Prophets, then those who are best after them in righteousness. Every person is tested according to his religious commitment. If he is strong in his religion, his trials will be more severe, and if he is weak in his religion, he will be tested according to his strength. The trials continue to befall a person until he walks upon the earth with no sin left upon him."