Question: The words “Whoever inaugurates a bad practice…”—are these the continuation of the hadith, or are they merely an analogy?
Answer: They are indeed the continuation of the hadith. They stand in direct opposition to “…whoever inaugurates a good practice,” for it goes on to say: “Whoever inaugurates a bad practice in Islam,” that is, someone who perpetrates an evil deed and becomes a harmful example for others—whether by abandoning obligations, committing prohibitions, introducing innovations, or the like.

“As for him, he bears its sin and the sin of all who act upon it:” whoever follows that practice carries the burden of this crime, and the initiator bears his own sin along with the sin of everyone who imitates him. This is the exact wording of the hadith.
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The meaning of the ḥadith of the strong believer
Question: What is the degree of authenticity of the hadith, “The strong believer is better and more beloved to Allah than the weak believer”? If it is authentic, what does it mean, and in what does strength lie?
Answer: First, the hadith is authentic; Imam Muslim related it in his Ṣaḥīḥ.

Its meaning is that the believer who is strong in faith, and strong in body and in deed, is better than the believer who is weak in faith or weak in his actions and physical strength. The strong believer produces and strives for the benefit of the Muslims. They gain tremendous advantage from his physical strength, his strength of faith, and his practical strength—through jihad in the path of Allah, through securing the Muslims’ interests, through defending Islam and the Muslims, through humiliating the enemies and standing firm against them—things the weak believer is unable to do. From this standpoint the strong believer is better than the weak believer, “yet there is good in each,” as the Prophet ﷺ said.