It is narrated from Sayyiduna Sabrah bin Fatik al-Asadi (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "The Balance is in the Hand of Allah; He raises some peoples and lowers others. And the heart of the son of Adam is between two of the fingers of the Most Merciful; if He wills He makes it deviate, and if He wills He keeps it upright."
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6527