Не плюй в колодезь, пригодится напиться

Never do harm to, or break friendly relations with people whose support you may need in future. See Не руби сук, на котором сидишь (H)

Var.: Не плюй в водицу: сгодится (случится) напиться. Не плюй в колодезь (колодец), пригодится воды напиться

Cf: Cast no dirt in the well that gives you water (Am.). Cast no dirt into the well that gives you water (Br.). Don't muddy the water, you may have to drink it (Br.). Don't throw dirt into the well that gives you water (Am., Br.). Let every man praise the bridge he goes over (Br.). Let every man speak well of the bridge that carries him over (Br.). Never cast dirt in the fountain that has given you refreshing drink (Am.). Never cast dirt into that fountain of which thou hast sometime drunk (Br.). Praise the bridge that carries you over (Am.)