Tripundra

[4] The allegorical significance of the "three ash lines", states Deussen, is that the tradition sees them as streaks of three Vedic fires, three audible syllables of AUM, three Guṇas, three worlds, three Atmans, trayi Vedas, and three aspects of Shiva.

[2] Tripundra, to those who apply it, is a reminder of the spiritual aims of life, the truth that body and material things shall someday become ash, and that mukti is a worthy goal.

Holy ash, remains from yagya or sacrificial fire-wood is a reminder of the temporary nature of the physical body and the importance of spiritual attainment and closeness to Shiva (Atman-Brahman).

Chapter 2 of Kalagni Rudra Upanishad explains the three lines as various triads: sacred fires, syllables of Om, gunas, worlds, types of atman (Soul), powers, Vedas, the time of extraction of the Vedic drink Soma, and Mahesvara (a form of Shiva).

[6][7] The "Tri" in the word Tripundra signifies the Triguna – Satva, Raja and Tama; Triloka – Bhuhu, Bhuvaha, Suvaha; Tritapa – Bbhoutika, Daivika, Adhyatmika.