And when he clarified that there is no escape from hardship except by this undertaking, he began to explain the obstacle, starting with emphasizing its significance due to its great value. He said, expressing in the past tense, which is the custom of the Qur'an that when it expresses it, it explains the inquiry about it: ﴿And what will make you know﴾, meaning, O listener to our words, desiring what is with us, ﴿what the obstacle is﴾, meaning, you have not known the essence of its difficulty and the greatness of its reward. When the heart became free by inquiring about what it does not know, and a person is most eager to know what has perplexed him, the souls yearned for its knowledge. He pointed to the first one, which is chastity, whose fruit is generosity, and the rectification of the power of desire, expressing by the release, which is the least of what can be from emancipation, because it is assistance in it, even if it is little, as has been reported in the hadith of Al-Bara, may Allah be pleased with him: 'Emancipate the soul and release the neck.' And its emancipation is to be free from it, and its release is to be specified in its price. He explained the intended meaning of this obstacle with what indicates a measure that is not as it comes to specify its estimation, for it is not used except repeatedly.