Is it permissible to spend the money designated for Hajj on a commercial project for an unemployed son, knowing that the opportunity for Hajj might be delayed due to the lottery system, and would it be considered a major sin if one dies before performing the obligation?

The majority of scholars hold that one must hasten to perform Hajj immediately upon possessing sufficient funds for it. It is impermissible to dispose of this money by giving it to a son or anyone else once the time for Hajj becomes obligatory. This obligatory time is when the people of a given locality set out for Hajj, or when one applies for the Hajj lottery, as applying for the lottery is essential for fulfilling the obligation of Hajj. However, before the time for applying for the lottery, there is no harm in disposing of the money because Hajj has not yet become obligatory. But if the time for departure arrives and the money is available, Hajj becomes obligatory, and it is not permissible to spend the money on anything else.