Chandogya Upanishad
samastasya khalu sāmna upāsanaṃ sādhu yat khalu sādhu tat sāmety ācakṣate yad asādhu tad asāmeti
Meditation on the whole of the Sâman is good, and people, when anything is good, say it is Sâman; when it is not good, it is not Sâman.
tad utāpy āhuḥ sāmnainam upāgād iti sādhunainam upāgād ity eva tad āhuḥ asāmnainam upāgād ity eva tad āhuḥ
Thus they also say, he approached him with Sâman, i.e. becomingly; and he approached him without Sâman, i. e. unbecomingly.
athotāpy āhuḥ sāma no bateti yat sādhu bhavati sādhu batety eva tad āhuḥ asāma no bateti yad asādhu bhavaty asādhu batety eva tad āhuḥ
And they also say, truly this is Sâman for us, i.e. it is good for us, when it is good; and truly that is not Sâman for us, i. e. it is not good for us, when it is not good.
sa ya etad evaṃ vidvān sādhu sāmety upāste 'bhyāśo ha yad enaṃ sādhavo dharmā ā ca gaccheyur upa ca nameyuḥ
If any one knowing this meditates on the Sâman as good, depend upon it all good qualities will approach quickly, aye, they will become his own.