Every morpheme-addition to the structure of hadith terms, necessarily provides additional meaning to these words. This confirms the direct impact of the morpheme additions in enriching the argumentation and the independent reasoning (Ijtihad) in line with the purposes of Islamic Sharia. And because of it, there are many issues of legitimacy were decided and addressed, in which some scholars were confirmed and trusted while some others were denied. This is exactly what calls for the necessity to shedding light on this important issue, investigating it, revealing its implications, and then reaching the extent of convergence between the Musnad of Al-Rabi` and other books of the Sunnah. In order to answer the study questions, I traced and extrapolated the additional morpheme of words that were only found in the Musnad of Al-Rabi compared to the two Sahihs; in order to elicit their implications, and compare the facets of agreement and disagreement among scholars regarding the interpretation of these additional morphemes of words. The study's objectivity is limited to tracing the hadiths of the Musnad in its first and second parts and to editing what came as an additional morpheme to its words. This is in case that these additions had an impact on the difference of the provisions of Islamic law -even if it is by the opposition in meaning according to the narrations of the two Sahihs for the same subject. Whether that morpheme-added narration was brought out by Al-Bukhari and Muslim or by one of them. The study was divided into an introduction that provides the definition of some hadith concepts such as boosting the trust and its divisions, as well as a translation of the three Imams. Two chapters of the study discuss the morpheme-additions of the words of Al-Rabi` Musnad compared to the two Sahihs, in all chapters of the Musnad. I divided each chapter into several sections, each section examines a specific provision of Islamic law in terms of hadith and worship. I concluded my study with an appendix of what I thought should be excluded from the additional-morphemes hadiths, although I did not find them to have a real impact in the differences of scholars' opinions. The most important findings of the study: - The study proved that the number of hadiths of Al-Rabi' which contain morpheme additions to the hadiths of Al-Bukhari and Muslim are very few compared to the hadiths on which the three agreed. - All the morpheme additions of words that affect the different opinions of scholars in al-Rabi`s upon that of al-Bukhari and Muslim are acceptable and valid additions, and this has been suggested through this research.