Birds of a feather flock together

ययोरेव समं वित्तम्
ययोरेव समं कुलम् ।
तयोः सख्यं विवाहश्च
न तु पुष्टविपुष्टयोः ॥

- महाभारतम्

- पञ्चतन्त्रम्

Friendship or marriage is possible only between those who are equal in wealth as well as family status, and not between rich and poor.

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Birds of a feather flock together.