Srimad Bhagavatam Canto 11, Chapter 16, Text 30

SB 11.16.30

ratnanam padma-rago ’smi
 padma-kosah su-pesasam
kuso ’smi darbha-jatinam
 gavyam ajyam havihsv aham
 
Translation: 
 
Among jewels I am the ruby, and among beautiful things I am the lotus cup. Among all types of grass I am the sacred kusa, and of oblations I am ghee and other ingredients obtained from the cow.
 
Purport: 
 
Pañca-gavya refers to five sacrificial ingredients obtained from the cow, namely milk, ghee, yogurt, dung and urine. The cow is so valuable that even its dung and urine are antiseptic and fit for sacrificial offering. Kusa grass is also used for religious occasions. Maharaja Pariksit constructed a sitting place from kusa grass during the last week of his life. Among beautiful things the lotus cup formed by lotus petals represents Lord Krsna, and among jewels the ruby, which is similar to Lord Krsna’s own Kaustubha gem, symbolizes the potency of the Lord.
Srimad Bhagavatam Canto 11, Chapter 16, Text 29
Srimad Bhagavatam Canto 11, Chapter 16, Text 31