Or HaChaim on Numbers 11:14/אור החיים על במדבר י״א:י״ד

1 לא אוכל אנכי לבדי לשאת, I cannot carry (this burden) all by myself." Here Moses revealed his own wishes in the matter. He told G'd that his refusal to carry the load all by himself was not due to lack of good will to carry out G'd's assignment but to his conviction that it was beyond his ability to do so.