Albert Barnes on Matthew 10:16

As sheep in the midst of wolves. That is, I send you, inoffensive and harmless, into a cold, unfriendly, and cruel world. Your innocence will not be a protection.

Be wise as serpents, etc. Serpents have always been an emblem of wisdom and cunning, Gen 3:1. The Egyptians used the serpent in their hieroglyphics as a symbol of wisdom. Probably the thing in which Christ directed his followers here to imitate the serpent was in its caution in avoiding danger. No animal equals them in the rapidity and skill which they evince in escaping danger. So said Christ to his disciples, You need caution and wisdom, in the midst of a world that will seek your lives. He directs them also to be harmless, not to provoke danger, not to do injury, and thus make their fellow-men justly enraged against them. Doves are, and always have been, a striking emblem of innocence. Most men would foolishly destroy a serpent, be it ever so harmless; yet few are so hard-hearted as to kill a dove.

(f) "wise as serpents" Rom 16:19, Eph 5:15 (1) "harmless" or, "simple" (g) "as doves" Php 2:15