greatest treasure among treasures

ऋतस्य दातारम् अनुत्तमस्य निधिं निधीनां चतुरन्वयानाम्

ये नाद्रियन्ते गुरुम् अर्चनीयं पापान् लोकान् ते व्रजन्त्यप्रतिष्ठान्

ṛtasya dātāram anuttamasya nidhiṁ nidhīnāṁ caturanvayānām 

ye nādriyante gurum arcanīyaṁ pāpāān lokān te vrajantyapratiṣṭhān 

Mahaabharatham Aaadiparvam (Sambhava parvam) chapter 71 

ഋതസ്യ ദാതാരം അനുത്തമസ്യ നിധിം നിധീനാം ചതുരന്വയാനാം 

യേ നാദ്രിയന്തേ ഗുരും അര്‍ച്ചനീയം പാപാന്‍ ലോകാന്‍   തേ വ്രജന്ത്യപ്രതിഷ്ഠാന്‍ 

They that, having acquired knowledge, injure their preceptor who is always an object of worship, who is the giver of knowledge, who is the most precious of all precious objects on Earth, come to be hated on Earth and finally go to the regions of the sinful.' 

This is a statement by Kacha as told to his guru, Sukraacharya. Kacha has come to learn the 

Sanjeevini Vidya (bringing back to life a dead person) from Sukracharya. The asuraas knowing that Kacha the son of Brihaspathi was a deva and hated him. They tried to kill him in many ways, but through the intervention of Devayani Sukra's daughter, the guru rejuvenated him to life. Finally, the asuras killed him, burnt him to ashes, and mixed these ashes to the intoxicant drink which Sukracharya used to take. Sensing the absence of Kacha and the evil attitude of the asuras, Devayani once again requested her father to bring back Kacha to life. But now the acharya realized that the remains of Kacha were lying in his stomach and if he used the  Sanjeevani vidya, Kacha would come out destroying Sukra's body and causing his death. So after much deliberation Sukra taught the Sanjeevini Vidya to Kacha whom he had revived in his stomach and asked him to come out splitting the Guru's body but requested that he should use the Sanjeevani vidya to revive Sukra. While assuring that he would definitely do it, Kacha says these words. The Guru, who is the greatest treasure one can have, who has imparted all the knowledge to the disciple, is an object of worship, and if his desires are not fulfilled by the disciple the latter would be berated by all while he is alive and on death finally he will reach hell. And Kacha kept his promise and revived Sukra.