What is the ruling on using a Hadith without a chain?

In the Name of Allah, the Most Gracious, the Most Merciful.  

Assalāmu ῾alaykum wa Rahmatullāhi Wabarakātu

Your question is not clear.

Do you mean using a hadith that does not have a chain of narrators and the authenticity of the hadith is unknown or do you mean narrating a hadith without its known chain of narrators.

In the first case, it is not permissible to narrate a hadith, the authenticity of which is unknown.

In the second case if the authenticity of the hadith is known and recorded in the reliable books of hadith, it is not necessary to narrate the entire Sanad when quoting such Ahadith. In that case we rely on the recorded chain of narrators. [1]

And Allāh Ta῾āla Knows Best

Wassalāmu ῾alaykum 

Jibran Kadarkhan

Student Dārul Iftā

Mauritius

Checked and Approved by:

Mufti Ebrahim Desai

[1]

 (  نخبة الفكر :(162-164,دار الرقم

تحفة الدرر: (22-20, دار العصر الجديد للنشر)