Or HaChaim on Deuteronomy 1:12/אור החיים על דברים א׳:י״ב

1 איכה אשא לבדי, "How can I bear alone, etc.?" Moses now reverts to what he had said in verse 9: "I cannot bear you myself alone." He had interrupted this train of thought in order to counteract any negative results which would accrue to the people from a complaint about them by their leader. At this point he feels it is safe to carry on with what he had to say in verse 9.