after prophet Mohammad, his ahl-ul-bayt are well-grounded in knowledge.”
who are immaculate and God purified them and chooseed them for guidance of people after prophet.
God says in the last part of verse 33 in chapter 33 in the holy quran:
Allah only desires to keep away the uncleanness from you, O people of the House! and to purify you a [thorough] purifying.
and about the book which i sent its link, you can download it and use it freely and also share it to others and mention its source.
you can download its pdf from this link:
https://www.al-islam.org/printpdf/book/export/html/30482
and also every one can donate to this website if desires.