Ibn Kathir (Abridged)
Hafiz Ibn KathirAllah's Love is Attained by Following the Messenger
This honorable Ayah judges against those who claim to love Allah, yet do not follow the way of Muhammad . Such people are not true in their claim until they follow the Shari`ah (Law) of Muhammad and his religion in all his statements, actions and conditions. It is recorded in the Sahih that the Messenger of Allah ﷺ said,«مَنْ عَمِلَ عَمَلًا لَيْسَ عَلَيْهِ أَمْرُنَا فَهُوَ رَد»(Whoever commits an act that does not conform with our matter (religion), then it will be rejected of him.)This is why Allah said here,قُلْ إِن كُنتُمْ تُحِبُّونَ اللَّهَ فَاتَّبِعُونِى يُحْبِبْكُمُ اللَّهُ(Say (O Muhammad to mankind): "If you (really) love Allah, then follow me, Allah will love you...") meaning, what you will earn is much more than what you sought in loving Him, for Allah will love you. Al-Hasan Al-Basri and several scholars among the Salaf commented, "Some people claimed that they love Allah.
So Allah tested them with this Ayah;قُلْ إِن كُنتُمْ تُحِبُّونَ اللَّهَ فَاتَّبِعُونِى يُحْبِبْكُمُ اللَّهُ(Say (O Muhammad to mankind): "If you (really) love Allah, then follow me, Allah will love you..."). "Allah then said,وَيَغْفِرْ لَكُمْ ذُنُوبَكُمْ وَاللَّهُ غَفُورٌ رَّحِيمٌ("And forgive you your sins. And Allah is Oft-Forgiving, Most Merciful.") meaning, by your following the Messenger , you will earn all this with the blessing of his mission. Allah next commands everyone,قُلْ أَطِيعُواْ اللَّهَ وَالرَّسُولَ فإِن تَوَلَّوْاْ(Say: "Obey Allah and the Messenger." But if they turn away) by defying the Prophet)فَإِنَّ اللَّهَ لاَ يُحِبُّ الْكَـفِرِينَ(then Allah does not like the disbelievers.) thus, testifying that defiance of the Messenger's way constitutes Kufr. Indeed, Allah does not like whoever does this, even if he claims that he loves Allah and seeks a means of approach to Him, unless, and until, he follows the unlettered Prophet, the Final Messenger from Allah to the two creations: mankind and the Jinn.
This is the Prophet who, if the previous Prophets and mighty Messengers were to have been alive during his time, they would have no choice but to follow, obey him, and to abide by his Law. We will mention this fact when we explain the Ayah,وَإِذْ أَخَذَ اللَّهُ مِيثَـقَ النَّبِيِّيْنَ(And (remember) when Allah took the Covenant of the Prophets) 3:81, Allah willing.