These two terms have a common meaning and are repeated here for emphasis. They can be combined. Alternate translation: "Keep watch" (See: [[rc://en/ta/man/translate/figs-doublet]])
Here Jesus is speaking to his disciples in a metaphor they do not understand. Jesus is comparing the Pharisees' and Herod's teachings to yeast, but you should not explain this when you translate it because the disciples themselves did not understand it. (See: [[rc://en/ta/man/translate/figs-metaphor]])