Shiva Purana
ये शिवज्ञानवक्तारं निन्दंति च तपस्विनम् ॥ गुरून्पितॄनथोन्मत्तास्ते यांति निरयार्णवम् ॥ ८॥
Those who censure the propounder of Śiva’s perfect knowledge, ascetics, preceptors or parents are mad. They fall into the ocean of hell.
english translation
ye zivajJAnavaktAraM nindaMti ca tapasvinam ॥ gurUnpitRRnathonmattAste yAMti nirayArNavam ॥ 8॥
hk transliteration by Sanscript