(56) “Indeed, you do not guide whom you love, but Allah guides whom He wills, and He knows best those who are guided.”
Allah Most High informs you, O Muhammad—and, all the more so, everyone else—that you have no power to guide anyone, even if he is among the people dearest to you. This is beyond the power of created beings: it is the guidance of divine enablement and the creation of faith in the heart. That lies solely in the hand of Allah, Glorified and Exalted. He guides whomever He wills, and He knows best who is fit for guidance and therefore guides him, and who is unfit for it and therefore leaves him in his misguidance.
As for guidance being ascribed to the Messenger in the words of Allah Most High, “And indeed, you surely guide to a straight path,” that is the guidance of clarification and instruction. The Messenger makes the straight path clear, encourages people to follow it, and exerts his utmost effort to lead creation along it. But as for creating faith in their hearts and actually enabling them to embrace it—far be it from him; never!