Praise be to Allah. Al-Bukhaari (8) and Muslim (12) narrated that Ibn ‘Umar (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Islam is built on five (pillars): the testimony that there is no god but Allah and that Muhammad is the Messenger of Allah, establishing prayer, giving zakaah, Hajj and fasting Ramadan.” The shahaadatayn (twin testimony of faith) is one of the pillars of Islam, and this first pillar of Islam is a belief that includes affirming the oneness of Allah and testifying to the message of His Prophet. The conjunction wa (“and”) indicates that the two phrases come under the same ruling, which applies equally to both. Just as it is obligatory for an individual to say “I bear witness that there is no god but Allah (ash-hadu an laa ilaaha ill-Allah),” and his Islam is not valid, and he has not entered Islam, unless he says that, the same ruling applies equally to the second half of the shahaadah (testimony of faith): “I bear witness that Muhammad is the Messenger of Allah (ash-hadu anna Muhammadan rasool-Allah).” So the individual must also say this, and his Islam is not valid, and he has not entered Islam, unless he says it. So these two phrases are equally subject to the ruling, and they are the two halves of a single pillar of Islam, which is the Shahaadatayn (twin declaration of faith).