In plain words
Mere knowledge of the scriptures and mere knowledge of experience are both incomplete
A man setting out on a journey to another village found a river blocking his way midway. It was in flood and overflowing. The traveller tried to cross. Since he knew neither the way nor the depth, he looked this way and that. As two people were sitting under the trees in the distance, he went there and looked. There one was lame and the other blind. Thinking that they did not know the depths and shallows and that their words should not be trusted, he went back. That is, one without knowledge of the scriptures is the blind man, one without knowledge of experience is the lame man. Mere knowledge of the scriptures and mere knowledge of experience are incomplete. Only when the two come together is one complete. He alone can uplift the disciple. This is a saying of the Muṇḍaka Upaniṣad.