Is it permissible to withhold some of the sayings of the Messenger of Allah, peace and blessings be upon him, such as the hadith "The Right of the Husband Over His Wife," or the hadith of the fly, or the hadith of breastfeeding the elder, on the pretext that they do not suit the current era or because they contain certain words?

The fundamental principle is to convey and disseminate the knowledge of the Quran and Sunnah. It is incorrect to describe anything firmly established in the Sunnah as unfitting for the current era, for it is as binding as the Quran in the obligation to convey it and act upon it. As for texts whose understanding poses a challenge, it is left to the discretion of the scholars to determine when, to whom, and how to speak about them. Indeed, a scholar may refrain from discussing certain matters if he fears discord or that the questioner may not comprehend.