Be mindful with a minor Mitzva [commandment] as with a major commandment.
“A minor Mitzva” means that it seems to a person that this is something not very important, which is faith, since it is something that is above reason, and faith does not require much knowledge because it is only acceptance in the heart and not attainment in the mind.
“A major Mitzva” means that which a person knows is important because he knows that not every person is rewarded with attainment.
Therefore, with matters pertaining to attainment, a person walks carefully, lest he will not acquire the attainment. Or, only in matters by which one can achieve knowledge can one exert because it is worthwhile for him, but things that pertain to faith are trivial in his eyes and he cannot overcome his laziness, to make it worth his while to exert for something not very important.
This is why they said, “Be mindful with a minor Mitzva [commandment] as with a major one, for you do not know the reward given for Mitzvot [commandments].”
A person thinks that receiving the reward is from something that gives contentment above. Hence, when he learns and finds success in his learning, meaning that he has vitality and can present innovations in the Torah, or feels while he prays that he has love and fear and Dvekut [adhesion] and excitement during the prayer, at that time he is mindful about the matter and wants to continue his work.
Although he sees that he has no time and he is preoccupied, he still has the strength to give even to the point of devotion so as not to rest from Torah and from prayer, since he feels in this knowledge, meaning he knows and feels on himself that these Torah and prayer give contentment above. Hence, at such a time he is mindful to do his work however he can.
This is not so with a minor Mitzva, which is only by acceptance of the burden of the kingdom of heaven, where he does not feel a flavor in the Torah, and where he has no vitality in the prayer. At such a time, it is regarded as “minor.”
When he has no importance for such work, he does not want to be mindful and overcome the disturbances he has because he says that in any case, the engagement in Torah and Mitzvot is not so important above when he has no vitality. He wants to stop over a small disturbance because above it is also unimportant and he will not receive a great reward.
Therefore, they said, “You do not know the reward given for Mitzvot.” In other words, the Creator derives contentment from his state of Katnut [smallness/infancy], which is only by acceptance of the burden of the kingdom of heaven without any knowledge, intellect, or other feeling from the time of Gadlut [greatness/adulthood], as his importance above is mainly the work during the Katnut, and not the Gadlut.
Because a person does not know which state gives more contentment above, “Be mindful with a minor Mitzva,” meaning in the state of Katnut, “as with a major one,” namely in the state of Gadlut.