If the blind lead the blind both shall fall into the ditch

Russian translation

Если слепой ведет слепого, оба свалятся в канаву.
Если несведущий человек берется давать советы такому же несведущему или руководить им, то это приводит к печальным последствиям для обоих.

Derivation

The blind leading the blind.

Comparison

Слепой слепца водит, оба ни зги не видят.
Слепого в вожаки не берут.
Косой кривого не учит.

Examples

It is written, When the blind lead the blind, both shall fall into the ditch: wherefore, in such circumstances, may it not sometimes be safer, if both leader and led simply - sit still? (Carlyle)

They walked along without any particular destination, but simply for the sake of walking through this soft cool night. Coleman ld the way, tapping the pavement at every step with the ferrule of his stick. "The blind leading the blind," he explained. "Ah, if only there were a ditch, a crevasse, a great hole full of stinging centepides and dung. How gleefully I should lead you all into it!" (Huxley)

If only ... books were sold by men of taste, familiar with their contents, the public would buy more good literature: as things are, the blind bookseller leads the blind customer. (Squire)