مَا ضَلَّ صَاحِبُكُمْ وَمَا غَوَىٰ (your companion [ the Holy Prophet ﷺ ] has neither missed the way, nor did he deviate. [ 53:2] Verse [ 1] was قَسَم qasam or oath and verse [ 2] is jawab-ul-qasam or the subject for which oath is sworn. The verse means that the path towards which the Holy Prophet ﷺ is calling the people is the perfectly straight path leading to the desired goal of Allah's good pleasure. He is following the right guidance and has not deviated from the path of righteousness.
The Reason for Describing the Holy Prophet ﷺ as 'your companion'
The Qur'an on this occasion, when referring to the Holy Prophet ﷺ ، does not refer to him by his blessed name or refer to him as a Messenger or a Holy Prophet ﷺ . In fact, it refers to him as Sahibukum or "your companion". In this there seems to be a subtle rebuke to the pagans of Makkah, telling them in effect that the Holy Prophet ﷺ is not an outsider, nor a stranger to them. He was their constant companion. He was born amongst them, he spent his childhood amongst them, and he grew up as a youth amongst them. He has lived among them a whole life-time, and they had always looked upon him as a paragon of honesty, integrity and truthfulness calling him اَمِین (The Honest One). But now - after his claim of Prophethood - they dare impute to him such a heinous sin as forging lies against Allah. A man who withheld himself from telling lies about men, how could he possibly forge lies against Allah? How inconsistent is their attitude?