Heera soi saraahiye, from movie Highway (2014)

हीरा सोई सराहिये सहे घनन की चोट,
कपट कुरंगी मानवा परखत निकरा खोट ॥ Bijak/Sakhi 168 ||
Admire the diamond that can bear the hits of a hammer.
Many deceptive preachers, when critically examined, turn out to be false.
[Here diamond is siddhanta (the basic principles or doctrine).An experienced diamond cutter can hit the diamond using a chisel so that the chips will break off as expected. A diamond because if its crystalline structure tends to break off at specific angles. Similarly the true doctrine would come out shining when it is critically examined].

हीरा तहाँ ना खोलिए जहाँ कुँजड़ो की हाट,
सहज गाँठि बांधि के लगिए अपनी बाट ॥ Bijak/Sakhi 170 ||
Don't open your diamonds in a vegetable market.
Tie them in bundle and keep them in your heart, and go your own way.
[Don't discuss gyan (knowledge) with those who can not understand it].

हीरा परा बजार में रहा छार लपटाय,
केतिहे मूरख पचि मुए कोई पारखी लिया उठाय ॥ Bijak/Sakhi 171 ||
A diamond was laying in the street covered with dirt.
Many fools passed by. Someone who knew diamonds picked it up.
[Those who understand gyan-siddhanta (true knowledge/principles), pause to acquire it].


Reference (borrowed from) : http://www.cs.colostate.edu/~malaiya/kabir.html