What is the detailed explanation of the phrase: "The author said: 'Or he intends with his purification to permit something like prayer. This is for other than the one with constant ritual impurity (da'im al-hadath); as for him, the intention of permitting [prayer] is obligatory for him, but the one with constant ritual impurity does not need to specify the intention of a fard (obligatory act), unlike tayammum (dry ablution)'"?

The clarification of the phrase is summarized as follows: The one performing purification intends to remove the impurity (hadath (definition)) or to be permitted to pray. For someone whose impurity is continuous (like one afflicted with incontinence), their intention is to be permitted to pray, not to remove the impurity. As for tayammum (definition) (dry ablution), according to the relied-upon position in the Hanbali madhhab (definition), it requires specifying the intention for the obligatory prayer. So, whoever intends a supererogatory prayer or makes a general intention does not become permitted to perform the obligatory prayer with it. However, those who hold that tayammum removes impurity do not stipulate this specification.