From the signs that one is blessed in his knowledge..

Sheikh al-Albaani رحمه الله  said:

The Scholars have said (that) from the signs that one is blessed in his knowledge is him referring points of benefits to the founder of it (such as the author or the translator or a reference to where one got the benefit from), because in doing that one frees himself from plagiarism as it is been brought to attention by the Prophet صلّى اللَّهُ عليه وسلّم in his statement: The one being satisfied with that he has not been given is as a person wearing two garments of deception.

(Bukari & Muslim)

{The Reference: The Preface of Sheikh Albaani from the Book: Kalimut Tayyib for Sheik-ul-Islaam bin Taymiyyah}