Yes, you're correct. Isnad refers to the chain of narrators or authorities who have transmitted a hadith from the original source down to the collector of the hadith. It is an integral part of the science of hadith authentication in Islam.

The tradition of validating the isnad or the chain of narrators is crucial in determining the authenticity and reliability of hadiths. Scholars meticulously scrutinize the reliability and trustworthiness of each narrator in the chain to ascertain the accuracy of the transmitted information.

By examining the isnad, scholars can identify and eliminate any weaknesses or doubtful narrators in the chain, ensuring the preservation of the hadith's authenticity. The strength of the isnad contributes significantly to the grading and classification of the hadith as Sahih (authentic), Hasan (good), or Da'if (weak).

The science of hadith, known as 'Ilm al-Rijal (the knowledge of men), focuses on thoroughly investigating the biographical details, moral character, and credibility of narrators in the isnad chain. This comprehensive evaluation helps determine the reliability of the hadith and its attribution to the Prophet Muhammad (Peace be upon him).

It is important to note that the isnad holds significant importance in distinguishing between authentic hadiths and fabricated ones. Scholars have spent centuries compiling and studying hadith collections, ensuring the preservation of the Prophet's teachings and guiding the Muslim community in matters of faith and practice.