What is the concept of righteousness (al-birr) and benevolence (al-ihsan) in the Quran and Sunnah?

The Prophet, peace and blessings be upon him, was asked about righteousness (al-birr), and he said: "Righteousness is good character." He was asked about excellence (al-ihsan), and he said: "Excellence is to worship Allah as if you see Him, and if you do not see Him, then know that He sees you." The meaning of righteousness (al-birr) has been mentioned in the Quran as being synonymous with piety (al-taqwa).