The blind leading the blind
Uninformed and incompetent people leading others who are similarly incapable.
This appears in the Bible, Matthew 15:14 - from Miles Coverdale's Bible, 1535:
Let they go, they are ye blynde leaders of ye blynde. Wha one blinde leadeth another, they fall both i ye diche.
Biblical citations of commonly used English phrases usually tend to be earlier than those from other sources. In this case the thought was probably inherited from the Upanishads - the sacred Hindu treatises, which were written between 800BC and 200 BC and first translated into English between 1816-19. From Katha Upanishad we have:
Abiding in the midst of ignorance, thinking themselves wise and learned, fools go aimlessly hither and thither, like blind led by the blind.
Pieter Bruegel's 1568 oil painting, often called The Parable of the Blind, is what appears to be a literal depiction of a line of blind people following each other and stumbling into a ditch, as forecast in Matthew 15. Little is known of Bruegel religious views and his intent in conveying any moral sense or figurative meaning, if indeed he had any such with this painting, is difficult to interpret.