Pāśupata-vrata Māhātmya: Dvādaśa-Liṅga Mahāvrata, Month-wise Dravya, and Pūjā-krama
रत्नानाम् अप्यलाभे तु हेम्ना वा राजतेन वा रजतस्याप्यलाभे तु ताम्रलोहेन कारयेत्
ratnānām apyalābhe tu hemnā vā rājatena vā rajatasyāpyalābhe tu tāmralohena kārayet
宝石が得られぬときは、黄金または銀によって作らせよ。銀すら得られぬときは、銅または鉄によって作らせるがよい。そうして、資具の不足によって主パティ(シヴァ)のリンガ礼拝が妨げられぬようにするのである。
Suta Goswami (narrating Shiva-puja vidhi as received in the Linga Purana tradition)
It establishes an authorized hierarchy of substitutes—gem, gold/silver, then copper/iron—showing that sincere Linga-puja should continue even when ideal materials are not obtainable.
By allowing substitutions, it implies Śiva as Pati is not confined to a particular substance; the Linga functions as a supported focus for devotion, where bhakti and right procedure matter more than luxury.
A practical rule of puja-vidhi (dravya-vikalpa): ensure continuity of worship by making or commissioning a Linga from available metals, removing external obstacles that can bind the pashu through pasha (limitation and neglect).