In the Pre-lslamic Period when the people assumed Ihram, they would enter their houses from the back. So Allah revealed:-- "And it is not righteousness that you enter houses from the back, but the righteous man is he who fears Allah, obeys His Orders and keeps away from what He has forbidden. So enter houses through their doors." (2.189)  

كَانُوا إِذَا أَحْرَمُوا فِي الْجَاهِلِيَّةِ أَتَوُا الْبَيْتَ مِنْ ظَهْرِهِ فَأَنْزَلَ اللَّهُ {وَلَيْسَ الْبِرُّ بِأَنْ تَأْتُوا الْبُيُوتَ مِنْ ظُهُورِهَا وَلَكِنَّ الْبِرَّ مَنِ اتَّقَى وَأْتُوا الْبُيُوتَ مِنْ أَبْوَابِهَا}  

When the Ansar performed the Pilgrimage, they did not enter their houses but from behind. A person from the Ansar came and he began to enter from his door but it was said to him (why he was doing something in contravention to the common practice of coming to the houses from behind). Then this verse was revealed." Piety is not that you come to the doors from behind" (ii. 189).  

سَمِعْتُ الْبَرَاءَ يَقُولُ كَانَتِ الأَنْصَارُ إِذَا حَجُّوا فَرَجَعُوا لَمْ يَدْخُلُوا الْبُيُوتَ إِلاَّ مِنْ ظُهُورِهَا قَالَ فَجَاءَ رَجُلٌ مِنَ الأَنْصَارِ فَدَخَلَ مِنْ بَابِهِ فَقِيلَ لَهُ فِي ذَلِكَ فَنَزَلَتْ هَذِهِ الآيَةُ {وَلَيْسَ الْبِرُّ بِأَنْ تَأْتُوا الْبُيُوتَ مِنْ ظُهُورِهَا}  

[Machine] About Bara'a, the Ansar used to enter the masjid not through its main gate but through its backdoor. Allah revealed the verse "It is not righteousness that you enter houses from the back" (Surah Al-Baqarah, 189).  

عَنِ الْبَرَاءِ كَانَتِ الْأَنْصَارُ إِذَا حَجَّتْ لَمْ تَدْخُلْ مِنْ أَبْوَابِهَا وَدَخَلَتْ مِنْ ظُهُورِهَا فَأَنْزَلَ اللهُ تَبَارَكَ وَتَعَالَى {وَلَيْسَ الْبِرُّ بِأَنْ تَأْتُوا الْبُيُوتَ مِنْ ظُهُورِهَا} [البقرة 189]