Sirach 6:7-9

New Revised Standard Version, Anglicised

⁷ When you gain friends, gain them through testing,
    and do not trust them hastily.
⁸ For there are friends who are such when it suits them,
    but they will not stand by you in time of trouble.
⁹ And there are friends who change into enemies,
    and tell of the quarrel to your disgrace.