What is the meaning of the حديث: "On the night of my Isra (Night Journey), I passed by people whose lips were being clipped with scissors of fire..."? And does it apply to one who spreads good and urges people towards it, while striving to act upon it, though sometimes failing to do so, out of love for people to gain reward and for sin to be lifted from him?

The hadith warns severely against someone who enjoins good but then abandons it, or who forbids evil but then commits it. Abandoning what is enjoined and committing evil are blameworthy in all circumstances, but enjoining good and forbidding evil makes the commission of sin more heinous. The blame in the hadith falls on committing prohibited acts, not on forbidding evil. Therefore, it is advised to continue calling to Allah, enjoining good, and forbidding evil, while striving to perform obligations and avoid prohibitions.