The Ka`bah is the First House of Worship
Allah said,
﴿Εφδψσ Γσζψσασ ΘσνϊΚς ζυΦφΪσ αφαδψσΗΣφ﴾
(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.
﴿ασαψσΠφμ ΘφΘσίψσΙσ﴾
(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, i
﴿γυΘσΗΡσίΗπ﴾
(full of blessing), sanctified,
﴿ζσευΟπμ αψφαϊΪσάασγφνδσ﴾
(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,
«Λυγψσ ΝσνϊΛυ ΓσΟϊΡσίϊΚσ ΗαΥψσασΗΙσ έσΥσαψφ‘ έσίυαψυεσΗ γσΣϊΜφΟ»
(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.