Islam is built on five (foundations), and Islam is words and deeds and increases and decreases. (No. Hadith: 7)
حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُوسَى قَالَ أَخْبَرَنَا حَنْظَلَةُ بْنُ أَبِي سُفْيَانَ عَنْ عِكْرِمَةَ بْنِ خَالِدٍ عَنْ ابْنِ عُمَرَ رَضِيَ اللَّهُ عَنْهُمَا قَالَ قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بُنِيَ الْإِسْلَامُ عَلَى خَمْسٍ شَهَادَةِ أَنْ لَا إِلَهَ إِلَّا اللَّهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللَّهِ وَإِقَامِ الصَّلَاةِ وَإِيتَاءِ الزَّكَاةِ وَالْحَجِّ وَصَوْمِ رَمَضَانَ
Abdullah ibn Musa told us that he had told us Hanzhalah ibn Abu Sufyan of 'Ikrimah ibn Khalid of Ibn 'Umar said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Islam is built on five (foundations); the testimony is no god but Allah, and indeed Muhammad is the Messenger of Allah, establishing prayer, giving zakah, hajj and fasting Ramadlan”.
Reference: Shahih Bukhari Bab Imam