Since it is written in books

purAnamityeva na sAdhu sarvam , na chApi kAvyam navamityavadyam
santaha parikshatart bhajante, muDhah parapratyayena buddhihi

पुरणमित्येव न साधु सर्वं न चापि काव्यं नवमित्यवद्यं |
सनः परीक्श्तरत भजन्ते मूढः परप्रत्ययेन बुद्दिः ||

– Unknown

Can be interpreted as :

Concepts need not be valid just because they are told in books (holy books especially ;-))), mythologies etc. Nor things are right if they are modern. Gentlemen test and then trust, fools believe what is told and written.

I don’t remember who wrote it, guess it is Brutruharai. This is the best spelling I can give for the quote here. If anyone finds better please comment. And also if you find a similar one.

Quote is quite relevant. People when can not justify what they are practicing and what they believe, just hold some outdated books responsible. “Since it is written in…”