To tread lightly.

Chaya or tree spinach (Cnidoscolus aconitifolius). / Bull or spurge nettle (Cnidoscolus stimulosus). / Carolina horsenettle (Solanum carolinense).

Alternative form of speak softly and carry a big stick

Do not boast or utter verbal threats, but do make others aware that you are prepared to use physical force if necessary.

Alternative form of speak softly and carry a big stick