Bhagavad Gita: Chapter 3/Verse 21

यद्यदाचरति श्रेष्ठस्तत्तदेवेतरो जनः ।
स यत्प्रमाणं कुरुते लोकस्तदनुवर्तते ॥३- २१॥

yadyadācarati śreṣṭhastattadevetaro janaḥ ।
sa yatpramāṇaṃ kurute lokastadanuvartate ॥3- 21॥

Whatever that one does is most excellent, indeed, this and that other person does whatever standard. The world follows that.  

Word-for-word translations

yadyad (pronoun) = whatever

ācarati (present tense, 3rd person, singular) = that one does

śreṣṭhas (superlative, masculine, nominative, singular) = most excellent 

tattad (pronoun, 3rd person) = this and that 

eva (adverb) (indeclinable) = indeed

itaras (masculine, nominative, singular) = other 

janas (masculine, nominative, singular) = a person 

sas (pronoun, 3rd person, singular) = that one

yad (pronoun, neuter, accusative, singular) = whatever

pramāṇaṃ (neuter, accusative, singular) = standard

kurute (present tense, 3rd person, singular) = does

lokas (masculine, nominative, singular) = the world 

tad (pronoun, neuter, accusative, singular) = that 

anuvartate (present tense, 3rd person, singular) = it follows