Allah encouraged His Prophet to pray in Masjid Quba' which, from the first day, was built on Taqwa, obedience to Allah and His Messenger , for gathering the word of the believers and as an outpost and a fort for Islam and its people. This is why Allah the Exalted said,

﴿لَّمَسْجِدٌ أُسِّسَ عَلَى التَّقْوَى مِنْ أَوَّلِ يَوْمٍ أَحَقُّ أَن تَقُومَ فِيهِ﴾

(Verily, the Masjid whose foundation was laid from the first day on Taqwa is more worthy that you stand therein (to pray).) in reference to the Masjid of Quba'. An authentic Hadith records that the Messenger of Allah said,

«صَلَاةٌ فِي مَسْجِدِ قُبَاءٍ كَعُمْرَة»

(One prayer in Masjid Quba' is just like an `Umrah.) It is recorded in the Sahih that the Messenger of Allah used to visit Masjid Quba' while riding and walking. Imam Ahmad recorded that `Uwaym bin Sa`idah Al-Ansari said that the Prophet went to Masjid Quba' and asked,

«إِنَّ اللهَ تَعَالَى قَدْ أَحْسَنَ عَلَيْكُمُ الثَّنَاءَ فِي الطُّهُورِ فِي قِصَّةِ مَسْجِدِكُمْ، فَمَا هَذَا الطُّهُورُ الَّذِي تَطَهَّرُونَ بِهِ؟»

(In the story about your Masjid, Allah the Exalted has praised you concerning the purification that you perform. What is the purification that you perform) They said, "By Allah, O Allah's Messenger! We do not know except that we had neighbors from the Jews who used to use water to wash with after answering the call of nature, and we washed as they washed.'' Ibn Khuzaymah collected this Hadith in his Sahih. Allah's statement,

﴿لَّمَسْجِدٌ أُسِّسَ عَلَى التَّقْوَى مِنْ أَوَّلِ يَوْمٍ أَحَقُّ أَن تَقُومَ فِيهِ فِيهِ رِجَالٌ يُحِبُّونَ أَن يَتَطَهَّرُواْ وَاللَّهُ يُحِبُّ الْمُطَّهِّرِينَ﴾

(Verily, the Masjid whose foundation was laid from the first day on Taqwa is more worthy that you stand therein (to pray). In it are men who love to clean and purify themselves. And Allah loves those who make themselves clean and pure.) This encourages praying in old Masjids that were built for the purpose of worshipping Allah alone, without partners. It is also recommended to join the prayer with the believing group and worshippers who implement their faith, those who perform Wudu' perfectly and preserve themselves from impure things. Imam Ahmad recorded that one of the Companions of the Messenger of Allah said that the Messenger of Allah led them in a Dawn (Subh) prayer in which he recited Surat Ar-Rum (chapter 30) and made mistakes in the recitation. When he finished the prayer, he said,

«إِنَّهُ يَلْبِسُ عَلَيْنَا الْقُرْآنَ أَنَّ أَقْوَامًا مِنْكُمْ يُصَلُّونَ مَعَنَا لَا يُحْسِنُونَ الْوُضُوءَ، فَمَنْ شَهِدَ الصَّلَاةَ مَعَنَا فَلْيُحْسِنِ الْوُضُوء»

(We sometimes make mistakes in reciting the Qur'an, there are people among you who attend the prayer with us, but do not perform Wudu' perfectly. Therefore, whoever attends the prayer with us let him make perfect Wudu'.) This Hadith indicates that complete purification helps in the performance of acts of worship and aids in preserving and completing them.

﴿أَفَمَنْ أَسَّسَ بُنْيَانَهُ عَلَى تَقْوَى مِنَ اللَّهِ وَرِضْوَانٍ خَيْرٌ أَم مَّنْ أَسَّسَ بُنْيَانَهُ عَلَى شَفَا جُرُفٍ هَارٍ فَانْهَارَ بِهِ فِى نَارِ جَهَنَّمَ وَاللَّهُ لاَ يَهْدِى الْقَوْمَ الظَّـلِمِينَ - لاَ يَزَالُ بُنْيَانُهُمُ الَّذِى بَنَوْاْ رِيبَةً فِى قُلُوبِهِمْ إِلاَّ أَن تَقَطَّعَ قُلُوبُهُمْ وَاللَّهُ عَلِيمٌ حَكِيمٌ ﴾

(109. Is it then he who laid the foundation of his building on Taqwa to Allah and His good pleasure better, or he who laid the foundation of his building on the brink of an undetermined precipice ready to crumble down, so that it crumbled to pieces with him into the fire of Hell. And Allah guides not the people who are the wrongdoers.) (110. The building which they built will never cease to be a cause of hypocrisy and doubt in their hearts unless their hearts are cut to pieces. And Allah is All-Knowing, All-Wise.)