Rashi explains: “If you walk with my laws – to toil in Torah.” This indicates that one should toil and exert himself to learn Torah. However, one should not feel that the Torah is a heavy burden that he must toil to carry.
The Dubno Magid zt”l explains this with a parable of two merchants who shipped their wares with the same wagon driver. One of the merchants sent a small box containing diamonds and precious gems, while the other one sent a very heavy box containing other types of merchandise. As he was unloading the boxes, the wagon driver mixed up the two packages and brought the heavy box to the diamond merchant. When the merchant saw the wagon driver approaching, he immediately understood that something was wrong. He said, “Why are you sweating and exerting yourself so much? My box is small and light. A small child could easily carry it. This must not be my box!”
The Dubno Magid uses this moshol to explain the verse (Yeshaya 43:22): “And you did not call Me, Yaakov, for you wearied of Me, Yisroel.” The Navi chastised Klal Yisroel for not fulfilling the mitzvos wholeheartedly and willingly. His proof of this was that they were exerting themselves and growing weary. If they had been serving Hashem properly, it would not have been wearisome and difficult, as is stated (ibid 40:31): “And those who put their hope in Hashem shall renew their strength, they shall raise wings as eagles; they shall run and not weary, they shall walk and not tire.”
In this vein, the Ohr Hachaim Hakadosh explains the pasuk (Bamidbor 23:21): “And no toil is seen in Yisroel” to mean that even though tzadikim use all their strength to learn Torah and do mitzvos, they do not become tired or weary. They don’t view their avodah as a toilsome burden. On the contrary, it is very pleasant for them.
Similarly, the Kobriner Rebbe zy”a explains the pasuk (Devarim 25:18): “And you were tired and exerted and you did not fear G-d” to mean that if someone becomes tired and worn out from serving Hashem, it is a sign that he does not fear Him, meaning that his avodah is not being done properly.
