(Christianity)
The four holy cities of Judaism: Jerusalem, Hebron, Safed, and Tiberius

Hinduism
There are four Vedas: Rigveda, Samaveda, Yajurveda and Atharvaveda. In Puruṣārtha, there are four aims of human life: Dharma, Artha, Kāma, Moksha. The four stages of life Brahmacharya (student life), Grihastha (household life), Vanaprastha (retired life) and Sannyasa (renunciation). The four primary castes or strata of society: Brahmana (priest/teacher), Kshatriya (warrior/politician), Vaishya (landowner/entrepreneur) and Shudra (servant/manual laborer). The swastika symbol is traditionally used in Hindu religions as a sign of good luck and signifies good from all four directions. The god Brahma has four faces. There are four yugas: Satya, Dvapara, Treta and Kali

Islam
Eid al-Adha lasts for four days, from the 10th to the 14th of Dhul Hijja. The four holy cities of Islam: Mecca, Medina, Jerusalem and Damascus. The four tombs in the Green Dome: Muhammad, Abu Bakr, Umar ibn Khattab and Isa ibn Maryam (Jesus). There are four Rashidun or Rightly Guided Caliphs: Abu Bakr, Umar ibn al-Khattab, Uthman ibn Affan and Ali ibn Abi Talib. The Four Arch Angels in Islam are: Jibraeel (Gabriel), Mikaeel (Michael), Izraeel (Azrael), and Israfil (Raphael)
There are four months in which war is not permitted: Muharram, Rajab, Dhu al-Qidah and Dhu al-Hijjah. There are four Sunni schools of fiqh: Hanafi, Shafi`i, Maliki and Hanbali. There are four major Sunni Imams: Abū Ḥanīfa, Muhammad ibn Idris ash-Shafi`i, Malik ibn Anas and Ahmad ibn Hanbal. There are four books in Islam: Taurait, Zaboor, Injeel, Quran.
Four-dimensional space is the highest-dimensional space featuring more than three regular convex figures: 

Two-dimensional: infinitely many regular polygons. Three-dimensional: five regular polyhedra; the five Platonic solids which are the tetrahedron, cube, octahedron, dodecahedron, and icosahedron. Four-dimensional: six regular polychora; the 5-cell, 8-cell or tesseract, 16-cell, 24-cell, 120-cell, and 600-cell. The 24-cell, made of regular octahedra, has no analogue in any other dimension; it is self-dual, with its 24-cell honeycomb dual to the 16-cell honeycomb.