Orchot Tzadikim
And what is the seventh trait? As it is said, "The sluggard will not plow, when winter setteth in" (Prov. 20:4). Rabbi Simon, the son of Yohai said, "This refers to one who did not study Torah in his youth and wants to study when he is old — he will be unable to do so. That is what is meant by, "He shall beg in harvest, and have nothing" (ibid.).