Musar zu Schemot 23:15

And now we will speak about the matter of punishment for the nullification of positive commandments: Our Rabbis, may their memory be blessed, said (Ketuvot 86b) [that] if [the court warned] someone to perform [the commandment of the] sukkah or [of the] palm branch (lulav) “and he does not do so, we strike, etc.” And they said (Rosh Hashanah 17a) that men who have never placed tefillin on their heads are called “rebellious Jews with their bodies,” and their punishment is more severe than one who transgresses once against a sin for which he is liable for excision. And they said [that] all whose sins are greater than his merits and among [his sins] is the sin of rebellious Jews with their bodies - for example, one who has never worn tefillin or one who was involved in transgressions such as forbidden sexual relations - descend and are judged in Gehinnom for twelve months. After twelve months, their body is finished; and their soul is burnt; and the wind spreads it under the soles of the feet of the righteous ones, as it is stated (Malachi 3:21), “And you shall trample the wicked to a pulp, for they shall be dust, etc.” And they said (Sanhedrin 99a), [that] one who is permissive (in his eyes) [regarding] positive commandments, such as one who belittles the intermediate days of the festival - which is from a positive commandment, as it is stated (Exodus 23:15), “You shall observe the Feast of Matsot” - has no portion in the world to come, even if possesses Torah and good deeds. And there is a general warning of a negative commandment, for all the positive commandments - as it is stated (Deuteronomy 13:1), “neither add to it nor take away from it.”