The Holy Prophet said: "My entire ummah will go to Paradise save one who denies." The Companions inquired: "0 Apostle of Allah! Who's the person who denies you"? He replied: "He who obeyed me entered Paradise, and he who disobeyed me and did not believe in me denied." (Mishkat)
In this Hadith the Holy Prophet states that whosoever does not act upon his holy statements is a denier and such a denier will not enter Paradise along with his ummah; for had he had perfect faith and had made him (the Prophet) his beloved sincerely, he would have loved each one of his statements and actions, and he would have acted according to them, but when he did not act upon the sunnahs, it becomes clear that he was a repudiator.
Though his repudiation is not like that of the disbelievers and the polytheists, he does share, to some extent, this quality with them and so he will be kept first in Hell along with his comrades; since he had imitated them and co-operated with them in the world, he will have to put up with them. The only difference is that while the infidels and the polytheists will have to live there (in Hell) forever, he will not live there always; the punishment of Hell will be proposed for him in proportion to the extent and time he had copied them and forsaken his Prophet's methods.
O Lord of the Universe! Bestow upon this ummah the grace to obey its true Prophet and save it from hell and enter it into Paradise along with the very first group of Your Beloved Prophet. Amen!