Bhagavad Gita Verse 17.7

भोजन भी सबको अपनी-अपनी प्रकृति के अनुसार तीन प्रकार का प्रिय होता है । और वैसे ही यज्ञ, तप और दान भी तीन-तीन प्रकार के होते हैं । उनके इस पृथक्-पृथक् भेद को तू मुझसे सुन|

O Arjuna, even one of the most important necessities in life for all beings, namely food, belongs under three categories. Similarly, customs such as religious sacrifices, all acts of self-discipline, and self-restraint as well as the giving of gifts, can all be individually placed under three separate divisions.