The offering of a single bel leaf to Shiva. Each of its eight verses ends ekabilvam shivarpanam - one bilva leaf, offered to Shiva - and the opening verse reads the three leaflets as the three gunas, the three eyes and the three weapons.
Why is the bel leaf so important to Shiva?
Because it is his own leaf, and the hymn says a single one offered with devotion destroys the sin of three births. The tradition is deliberately making the point that what Shiva accepts costs nothing - no gold, no elaborate puja, one leaf.
How should the leaf be offered?
A whole three-leaflet bilva patra, unbroken and undamaged as the hymn specifies, with the smooth side down, placed on the linga with water. A leaf already offered may be washed and offered again - bel is the one leaf the tradition permits that for.
When is it recited?
Mondays, Pradosh, through Shravan and at Maha Shivaratri, during the abhishek as the leaves are placed. It is short, so many recite it daily before the household lamp.
What if bel leaves are not available?
Recite the hymn anyway - the intention is accepted, and the tradition allows a washed leaf from a previous offering. The Shiva puja samagri page covers what else may substitute.
About the Bilvashtakam
The Bilvashtakam - eight verses on the glory of offering the sacred bilva (bel) leaf to Lord Shiva.
Meaning
Each verse describes the three-leafed bilva patra as embodying the three gunas, the trident and the three eyes of Shiva, and offers it at his feet seeking forgiveness for sins.
Benefits
Recited while offering bel leaves in Shiva worship, especially on Mondays and Shivratri, to wash away sins and earn Shiva's grace, health and prosperity.
The Bilvashtakam above is given in both Devanagari (Sanskrit) and Roman transliteration so you can read it in whichever script you are comfortable with - switch between the two using the buttons above, share the link, or download a PDF.
A stotram is a longer Sanskrit hymn of praise, not a forty-verse chalisa and not the lamp-song of an aarti. Browse every stotra on the Stotram index. For japa of a short formula use a mantra. The steps of worship around the recitation are in Puja Vidhi.