Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Allah Almighty said: When I test My believing servant and he does not complain about Me to those who visit him, then I free him from My confinement, grant him better flesh in place of his former flesh, likewise give him better blood in place of his former blood, and he resumes his deeds anew."