Birds of a feather flock together

मृगा मृगैः सङ्गमनुव्रजन्ति
गावश्च गोभिस्तुरगास्तुरङ्गैः ।
मूर्खाश्च मूर्खैः सुधियः सुधीभिः
समानशीलव्यसनेन सख्यम् ॥

- पञ्चतन्त्रम्

Deer are accompanied by deer, cows by cows and horses by horses. Similarly, fools befriend fools and wise people enjoy the company of wise. Friendship is natural among like-minded people with similar hobbies.

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Birds of a feather flock together.