What is the best place for i'tikaf? Cite evidence from the Holy Quran.

I‘tikaf (spiritual retreat) is not valid unless it is performed in a mosque, by the consensus of the jurists. The best mosques are Al-Masjid al-Haram, then Al-Masjid an-Nabawi, then Al-Masjid al-Aqsa. The jurists have agreed on the validity of I‘tikaf in a Jami’ mosque (a mosque where Friday prayers are held), and they differed concerning a non-Jami’ mosque. The preponderant opinion is the permissibility of I‘tikaf in it if congregational prayers are established therein.