Shaykh Muḥammad al-Jāmī:
The implementation of tawḥīd means to concentrate all of one’s devotion to Allah with clear intent, pure and free from the filth of shirk, bidʿah, and persistence upon sin. And if one slips [in this matter], he hastens to sincere repentance. So, whosoever is as such has indeed implemented tawḥīd.
The paramount aspect of this issue is that one has patience upon this [tawḥīd], such that he perseveres upon it in so that he meets Allah ﷻ whilst upon it, before being trialed with temptation. It could be that an individual is blessed with sincerity, an intense level of devotion and implementation of tawḥīd, however he may backslide – Allah’s ﷻ refuge is sought. For that reason actions are based upon the last deeds [of an individual], [meaning] this issue is conditional to his appointed time of death, such that he departs from the world upon this (tawḥīd) before backsliding or falling into temptation.
Due to this, ʿAbdullah ibn Maṣʿūd would say to his students: “Follow the way of those who have died [the scholars], emulate those who have died, for there is no guarantee that the one who is still alive will be saved from fitnah.” Whoever the individual it may be, there are many doors [leading] to fitnah [misguidance]. An individual is put to trial due to desires, doubts, craving for leadership, position, and having many followers. Fitnah is of various types. So whomever Allah ﷻ makes steadfast upon implementing tawḥīd until his appointed time of death, will enter paradise without reckoning nor punishment.