Shiva Purana
यथाग्निमानयेत्युक्ते ज्वलत्काष्ठादृते स्वयम् ॥ नाग्निरानीयते तद्वत्पूज्यो मूर्त्यात्मना शिवः ॥ १५ ॥
If some one says “Bring fire,” only the burning twig is brought. The fire by itself is not brought. In the same way Śiva is to be worshipped in the form of the idol.
english translation
yathAgnimAnayetyukte jvalatkASThAdRte svayam ॥ nAgnirAnIyate tadvatpUjyo mUrtyAtmanA zivaH ॥ 15 ॥
hk transliteration by Sanscript