It seems strange that we are told, by Jesus Himself, to be "wise as serpents" when the first thing most of us think of when it comes to serpents is Satan, who took the form of a serpent in the temptation of Eve. Many may not even realize this statement comes from Scripture, when most certainly it does. But what is Jesus saying to us, in context here? He's talking about when He is going to send them (the Apostles) out and that they would be persecuted for His sake. It would not be so wise to flaunt their Christianity in a world which, as He knew would be coming, persecutes Christians - simply because they believe in Jesus Christ as their Lord and Savior. Be cautious, and shrewd - and know when it is time to kick the dust from your sandals and move on to the next town.
Now what need is there to commend to you in many words the simplicity of the dove? For the serpent's poison had need to be guarded against: there, there was a danger in imitation; there, there was something to be feared; but the dove may you imitate securely. Mark how the doves rejoice in society; everywhere do they fly and feed together; they do not love to be alone, they delight in communion, they preserve affection; their cooings are the plaintive cries of love, with kissings they beget their young. Yea even when doves, as we have often noticed, dispute about their holes, it is as it were but a peaceful strife. Do they separate, because of their contentions? Nay, still do they fly and feed together, and their very strife is peaceful. See this strife of doves, in what the Apostle says,If any man obey not our word by this epistle, mark that man, and have no company with him.Behold the strife; but observe now how it is the strife of doves, not of wolves. He subjoined immediately,Yet count him not as an enemy, but admonish him as a brother.The dove loves even when she is in strife; and the wolf even when he caresses, hates. Therefore having the simplicity of doves, and the wisdom of serpents, celebrate the solemnities of the Martyrs in sobriety of mind, not in bodily excess, sing lauds to God. For He who is the Martyrs' God, is our Lord God also, He it is who will crown us. If we shall have wrestled well, we shall be crowned by Him, who has crowned already those whom we desire to imitate. (Sermon 14 on the New Testament).
16 Behold I send you as sheep in the midst of wolves. Be ye therefore wise as serpents and simple as doves. 17 But beware of men. For they will deliver you up in councils, and they will scourge you in their synagogues. 18 And you shall be brought before governors, and before kings for my sake, for a testimony to them and to the Gentiles: 19 But when they shall deliver you up, take no thought how or what to speak: for it shall be given you in that hour what to speak. 20 For it is not you that speak, but the Spirit of your Father that speaketh in you. 21 The brother also shall deliver up the brother to death, and the father the son: and the children shall rise up against their parents, and shall put them to death. 22 And you shall be hated by all men for my name's sake: but he that shall persevere unto the end, he shall be saved. (Matthew 10:16-22).
So go out there, preach the gospel - but don't be foolish about it! Persevere in Him and in simple communion with His Church. Do not be like the wolves who, as St. Augustine put it, even when they caress, they hate. Be like the doves, and commune in love.