It was narrated that 'Umar bin Khattab said:
"The Messenger of Allah said: 'There is no Muslim who performs ablution and does it well, then says: Ashhadu an la ilaha illallah, wa ashhadu anna Muhammadan `abduhu wa rasuluhu (I bear witness that none has the right to be worshipped but Allah, and I bear witness that Muhammad is His slave and Messenger),' (except that) eight gates of Paradise will be opened for him, and he will enter through whichever one he wants.'"
حَدَّثَنَا عَلْقَمَةُ بْنُ عَمْرٍو الدَّارِمِيُّ، حَدَّثَنَا أَبُو بَكْرِ بْنُ عَيَّاشٍ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَبْدِ اللَّهِ بْنِ عَطَاءٍ الْبَجَلِيِّ، عَنْ عُقْبَةَ بْنِ عَامِرٍ الْجُهَنِيِّ، عَنْ عُمَرَ بْنِ الْخَطَّابِ، قَالَ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏ "‏ مَا مِنْ مُسْلِمٍ يَتَوَضَّأُ فَيُحْسِنُ الْوُضُوءَ ثُمَّ يَقُولُ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَشْهَدُ أَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ إِلاَّ فُتِحَتْ لَهُ ثَمَانِيَةُ أَبْوَابِ الْجَنَّةِ يَدْخُلُ مِنْ أَيِّهَا شَاءَ ‏"‏ ‏.‏
GradeSahih (Darussalam)
English reference : Vol. 1, Book 1, Hadith 470
Arabic reference : Book 1, Hadith 508