From the Gnostic Gospel of Thomas, verse 21: ..."Therefore I say, if the
owner of a house knows that the thief is coming, he will begin his vigil
before he comes and will not let him dig through into his house of his
domain to carry away his goods. You, then, be on your guard against the
world. Arm yourselves with great strength lest the robbers find a way to
come to you, for the difficulty which you expect will (surely)
materialize. Let there be among you a man of understanding."