What is the meaning of al-wajadah? And what is its ruling?

The Shaykh : Finally: We come to the term "al-wajadah." Al-wajadah is a type of narration that Muslims in the early period sometimes needed, whereas Muslims today have no narration at all except through the path of al-wajadah. This is because you all know that there is no one in the Islamic world today who says, "So-and-so narrated to me, saying: So-and-so narrated to me, from so-and-so, saying: I heard," until the report reaches the Prophet (peace and blessings be upon him), and then he narrates it to people. The previous details—such as "narrated to us," "informed us," "told us," "I heard," and so on—no longer exist among Muslims except for narration through the path of al-wajadah. So we say, for example, "Al-Bukhari narrated in his Sahih," and how do we know? We saw it in his book. Therefore, our narration is solely through the path of al-wajadah. The scholars of hadith differed in the past regarding the validity of narration through al-wajadah, but the matter settled on a detailed distinction. If the book from which the one who found the hadith is quoting is a book whose attribution to its author is authentic, then this narration is valid. This is because the mind is reassured that so-and-so authored this book, and that the one who found the hadith is trustworthy in that he is quoting from a reliable book. This is the narration of al-wajadah, and it is what Muslims today, without exception, rely upon in what they transmit from books of hadith, tafsir, fiqh, and others.