The three lines of holy ash on forehead of a Hindu devotee has deep symbolism. Here are 9 symbolism of three lines of holy ash on forehead.
Upper line – atman
Middle line – antaratman
Lower line – Paramatman
Symbolic meaning – the self, the inner self and supreme self.
Upper line – kriyashakti
Middle line – icchashakti
Lower line – jnanashakti
Symbolic meaning – three powers of action, will and knowledge
Upper line – garhapatyagni
Middle line – dakshniagni
Lower line – ahavaniyagni
Meaning the three lines are the three household fires ever to be kept burning
Upper line – syllable A
Middle line – syllable U
Lower line – syllable M
Meaning the three measures of Pranava, OM (A, U, M)
Upper line – Rajas
Middle line – Sattva
Lower line – Tamas
Three attributes reflecting the strands of one’s disposition
Upper line – bhuloka
Middle line – Anatrikshaloka
Lower line – dyuloka
The three worlds of earth, intersphere and heaven
Upper line – Rig Veda
Middle line – Yajur Veda
Lower line – Atharva Veda
Symbolic meaning – the three vedas
Upper line – Pratassavanam
Middle line – Madhya
Lower line – Shayamasavanam – hnasavanam
Symbolic meaning – the morning, midday and evening rites in a day.
Upper line – Maheshwara
Middle line – Sadashiva
Lower line – Mahadeva
The three forms of Shiva