What is the ruling on fearing to fight the disbelievers and defend the sanctity of the religion, knowing that the questioner's soul shrinks from this, despite his attempts to remind himself of the verses of the Qur'an and the lessons therein?

What the questioner asks about falls under the jurisprudence of enjoining good and forbidding evil, not jihad. The controls for using force in forbidding evil are mentioned in Fatwa No. 122089. As for cowardice in fulfilling the right of Allah, its origin is the love of this world and the dislike of death, as in the Almighty's saying: {Have you not seen those to whom it was said, "Restrain your hands, establish prayer, and give zakat"? But when fighting was ordained for them, immediately a party of them feared men as they fear Allah or with [even] greater fear. They said, "Our Lord, why have You decreed upon us fighting? If only You had postponed us for a short time." Say, "The enjoyment of this world is little, and the Hereafter is better for he who fears Allah , and you will not be wronged, [even as much as] a thread."} (An-Nisa: 77) Fear of death is of two types: natural, which is not blameworthy, and blameworthy, which is weakness and reliance on this world. This latter type requires struggle by knowing that {The enjoyment of this world is little, and the Hereafter is better for he who fears Allah}, for the Hereafter is better than this world in essence, pleasure, and duration.