Birr is a theological concept in Islam which in essence is an internalised attitude of righteousness or goodness. Ayatul Birr gives the Divine concept of walking talking goodness.
It starts with the foundation being belief in Allah, the last day (Accountability), and Divine Guidance referring to the Angels, the Qur’an and the Messengers. This belief manifests itself through serving humanity and connecting to the Divine through Salaa and Zakaa. The human being who demonstrates Birr has the characteristics of being trustworthy, persevering, patient, God conscious and truthful.
The word BIRR comes from BARR which mean land just as BAHR means the sea. It denotes STABILITY and thus the foundation of BIRR (righteousness) is FIRM BELIEFS.
The aya was revealed when the qibla was changed from Baytul Muqaddas to the Ka’ba and there was a controversy regarding the change.