((إن أول بيت وضع للناس للذي ببكة مباركا و هدى للعالمين))
سـورة آل عـمران ٩٦

The Ka3bah is the First House of Worship

Allah said,

[إِنَّ أَوَّلَ بَيْتٍ وُضِعَ لِلنَّاسِ]

(Verily, the first House appointed for mankind) for all people, for their acts of worship and religious rituals. They go around the House [in Tawaf], pray in its vicinity and remain in its area in I`tikaf.

[لَلَّذِى بِبَكَّةَ]

(was that at Bakkah,) meaning, the Ka`bah that was built by Ibrahim Al-Khalil, whose religion the Jews and Christians claim they follow. However, they do not perform Hajj to the house that Ibrahim built by Allah's command, and to which he invited the people to perform Hajj. Allah said next,

[مُبَارَكاً]

(full of blessing), sanctified,

[وَهُدًى لِّلْعَـلَمِينَ]

(and a guidance for Al`Alamin.)

Imam Ahmad recorded that Abu Dharr said; "I said, `O Allah's Messenger! Which Masjid was the first to be built on the surface of the earth' He said, `Al-Masjid Al-Haram (in Makkah).' I said, `Which was built next' He replied `Al-Masjid Al-Aqsa (in Jerusalem).' I said, `What was the period of time between building the two' He said, `Forty years.' He added,

«ثُمَّ حَيْثُ أَدْرَكْتَ الصَّلَاةَ فَصَلِّ، فَكُلُّهَا مَسْجِد»

(Wherever (you may be, and) the prayer becomes due, perform the prayer there, for the whole earth was made a Masjid.)'' Al-Bukhari and Muslim also collected this Hadith.

The Names of Makkah, Such As Bakkah

Allah said,

[لَلَّذِى بِبَكَّةَ]

(was that at Bakkah), where Bakkah is one of the names of Makkah. Bakkah means, `it brings Buka' (crying, weeping) to the tyrants and arrogant, meaning they cry and become humble in its vicinity. It was also said that Makkah was called Bakkah because people do Buka next to it, meaning they gather around it. There are many names for Makkah, such as Bakkah, Al-Bayt Al-`Atiq (the Ancient House), Al-Bayt Al-Haram (the Sacred House), Al-Balad Al-Amin (the City of Safety) and Al-Ma'mun (Security). Makkah's names include Umm Rahm (Mother of Mercy), Umm Al-Qura (Mother of the Towns), Salah, [as well as others].

Source: tafsir.com