Is it part of the Sunnah to dress a newborn baby in clothes that have not been worn before, immediately upon their birth?

There is no authentic or weak hadith that commands a newborn to wear new clothes that have not been worn before, nor is there any basis for recommending that. The general rule regarding clothing is permissibility. Therefore, it is permissible to dress a newborn in used clothes, as long as it is not silk for males, or does not describe the 'awrah, based on the verse: (Say, "Who has forbidden the adornment of Allah which He has produced for His servants and the good things, pure, of provision?").