Across Sanatana Dharma the number seven (sapta) marks completeness and sacred order - seven cities that grant liberation, seven holy rivers invoked at every bath, seven sages who anchor each cosmic age, seven worlds above and below. These "sevens" are a quick map of the tradition's sacred geography, cosmology and lore.
The seven holiest cities - dying or doing sadhana in any of them is said to grant moksha. Each is tied to a deity or avatar (Ayodhya→Rama, Mathura/Dvaraka→Krishna, Kashi→Shiva, Kanchi→Devi/Shiva).
Ayodhyā Mathurā Māyā Kāśī Kāñcī Avantikā · Purī Dvāravatī caiva saptaitā mokṣadāyikāḥ
Invoked in the daily snana-mantra so that all seven rivers are present in one's bathing water. The Sarasvati is the sacred "hidden" river of the confluence at Prayag.
Gaṅge ca Yamune caiva Godāvari Sarasvati · Narmade Sindhu Kāveri jale'smin sannidhiṃ kuru
The seven seers of the current Manvantara - the stars of the Great Bear (Ursa Major). They anchor the gotra lineages of most Hindu families.
Saptarshis - full page →The seven ascending planes of existence, from the earth (Bhu) to the realm of Brahma (Satya). Below them lie the seven nether worlds (patalas).
Cosmography - 14 lokas →The seven "kula-parvatas", the principal mountain ranges of Bharatavarsha in the Puranic geography.
Seven beings granted deathlessness, said to live through the ages until the end of the Kali Yuga. A daily remembrance verse names them for long life. (Markandeya is often added as an eighth.)
Aśvatthāmā Balir Vyāso Hanūmāṃś ca Vibhīṣaṇaḥ · Kṛpaḥ Paraśurāmaś ca saptaite cirajīvinaḥ
The seven shaktis of the great gods, worshipped as a group especially in Shakta and Tantra traditions; they appear in the Devi Mahatmya battling Shumbha-Nishumbha.
Devi Mahatmya →The seven notes of the Indian musical scale, each traditionally linked to an animal cry and a deity. Music (Gandharva Veda) is itself a path to the Divine (nada-brahman).
Sangeet Shastra →