What was Imam’s motive behind writing a commentary on Forty Hadith?

Imam Khomeini: I, a humble servant of God, was contemplating for some time, to select forty hadith from among the ahadith of the members of the Household of the Prophet (peace be upon them) from the authentic books of the companions, and scholars, and was trying to compile them with an appropriate explanation of each of them that can be applied to the general conditions of the people.