Chapter on the Reasons Behind Hajj
Man Lā Yaḥḍuruh al-Faqīh|Volume 2|Book 3|Chapter 1
وَ وُضِعَ اَلْبَيْتُ فِي وَسَطِ اَلْأَرْضِ لِأَنَّهُ اَلْمَوْضِعُ اَلَّذِي مِنْ تَحْتِهِ دُحِيَتِ اَلْأَرْضُ وَ لِيَكُونَ اَلْفَرْضُ لِأَهْلِ اَلْمَشْرِقِ وَ اَلْمَغْرِبِ فِي ذَلِكَ سَوَاءً ».
The House (Ka'bah) was placed in the center of the Earth because it is the spot from beneath which the Earth was spread out, and so that its obligation could be equal for the people of both the East and the West.
- Ṣaḥīḥ al-Faqīh