Does the Hadith mean the impermissibility for Muslims to buy clothes before their old ones wear out, and did the Prophet do that?

The basic principle regarding clothing is permissibility, and nothing is forbidden from it except with evidence, based on the Almighty’s saying: ﴿Say, "Who has forbidden the adornment of Allah which He has produced for His servants and the good things, of provision?"﴾ [Al-A'raf: 32], and the Hadith: "Eat, give charity, and wear clothes, as long as extravagance and pride are avoided."

There is nothing in Islamic law that prohibits wearing new clothes before the old ones are worn out. What was narrated from Aisha, may Allah be pleased with her: "No new for him who does not wear the worn out," means that whoever is not gentle in using his clothes will have no new ones left, or no money left to buy new ones. This is part of being gentle and economical in livelihood, so it is recommended for a person to use old clothes in suitable places and situations to preserve the new ones and prolong their lifespan.