A ḥadīth (Arabic: حديث‎,  /ˈhædɪθ/ or /hɑːˈdiːθ/) (plural: hadith, hadiths, or aḥādīth) is a saying or an act or tacit approval or disapproval ascribed either validly or invalidly to the Islamic prophet Muhammad.

Hadith are regarded by traditional Islamic schools of jurisprudence as important tools for understanding the Quran and in matters of jurisprudence. Hadith were evaluated and gathered into large collections during the 8th and 9th centuries. These works are referred to in matters of Islamic law and history to this day. The two largest denominations of Islam, Shiʻism and Sunnism, have different sets of hadith collections.

In Arabic the word ḥadīth (Arabic: حديث‎ ḥadīṯ  IPA: [ħaˈdiːθ]) means 'a piece of information conveyed either in a small quantity or large'. The Arabic plural is أحاديث ʾaḥādīṯ/aḥādīth (IPA: [ʔaħaːˈdiːθ]). Hadith also refers to the speech of a person. As taḥdīṯ/taḥdīth is the infinitive, or verbal noun, of the original verb form; hadith is, therefore, not the infinitive, rather it is a noun.

Yusuf Estes (born in 1944) is an American Muslim preacher and teacher who converted from Christianity to Islam in 1991. He was a Muslim Chaplain for the United States Bureau of Prisons through the 1990s. He was a Muslim Delegate to the United Nations World Peace Conference for Religious Leaders held at the U.N. in September 2000.

Active in Islamic missionary work in the United States, Estes is often featured as guest presenter and keynote speaker at various Islamic events as well as frequently appearing on various Islamic satellite TV channels. Estes takes a dim view of today's public school system in the United States for any children, and highly recommends schools where they might receive a religious education combined with more advanced scholastic education.

Yusuf Estes was born in Ohio, and was raised in Houston, Texas in a Anglo-Saxon Protestant family. From 1962 to 1990, his career was in the music, entertainment and marketing fields. He also taught music and served as a music minister. He owned several musical instrument companies including the Estes Piano and Organ Company. He produced and directed live entertainment programs in the United States from the mid 1960s until his last endeavor for cable TV in Florida, entitled 'Estes Music Jamboree'.

Zakir Abdul Karim Naik (Urdu: ذاکر عبدالکریم نائیک; born 18 October 1965) is an Indian public speaker on the subject of Islam and comparative religion. He is the founder and president of the Islamic Research Foundation (IRF), a non-profit organisation that owns the Peace TV channel based in Dubai, UAE. He is sometimes referred to as a televangelist. Before becoming a public speaker, he trained as a doctor. He has written two booklets on Islam and comparative religion. He is regarded as an exponent of the Salafi ideology; he places a strong emphasis on individual scholarship and the rejection of "blind Taqlid", which has led him to repudiate the relevance of sectarian or Madh'hab designations, all the while reaffirming their importance.

Zakir Abdul Karim Naik was born on 18 October 1965 in Mumbai, India. He attended St. Peter's High School in Mumbai. Later he enrolled at Kishinchand Chellaram College, before studying medicine at Topiwala National Medical College and Nair Hospital and later the University of Mumbai, where he obtained a Bachelor of Medicine and Surgery (MBBS). His wife, Farhat Naik, works for the women's section of the IRF.