The meaning of Ashshahaadataini

The meaning of Ashshahaadataini
[i.e, Laa'ilaahailla-llahuMuhammadu-rrasulullahi]
They are the basic foundation of Islam and its first pillar, with which a person becomes a Muslim. So, whoever does not testify to them is not a Muslim.
Abdullah bin Umar (May Allah be please with them) narrated that the prophet (S.A.W) said:
«بُنِيَ الإِسْلاَمُ عَلَى خَمْسٍ: شَهَادَةِ أَنْ لا إله إلا اللهُ وَأَنَّ مُحَمَّدًا عَبْدُهُ وَرَسُولُهُ وَإِقَامِ الصَّلاَةِ وَإِيتَاءِ الزَّكَاةِ وَحَجِّ الْبَيْتِ وَصَوْمِ رَمَضَانَ» [متفق عليه].
Meaning: "Islam is built on five pillars: To testify that none is worthy of worship except Allah and that Muhammad is the messenger of Allah "Laailaa ill-Allah, Muhammadur-Rasulullah", to establish Salah (five daily prayers), to offer Zakah (obligatory charity), to perform Hajj (pilgrimage to Makah), and to fast the month of Ramadan. Agreed upon by Al Bukhari and Muslim.
Thus, the first thing that a person is supposed to learn in the religion of Islam is its first pillar, by knowing the meaning and rulings of Shahaadataini.
When the Prophet (s.a.w) sent Mu'adh ibnJabal to Yemen he said to him:
«إِنَّكَ سَتَأْتِي قَوْمًا أَهْلَ كِتَابٍ فَإِذَا جِئْتَهُمْ فَادْعُهُمْ إِلَى أَنْ يَشْهَدُوا أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ، وَأَنَّ مُحَمَّدًا رَسُولُ اللهِ فَإِنْ هُمْ أَطَاعُوا لَكَ بِذَلِكَ فَأَخْبِرْهُمْ أَنَّ اللَّهَ قَدْ فَرَضَ عَلَيْهِمْ خَمْسَ صَلَوَاتٍ فِي كُلِّ يَوْمٍ وَلَيْلَةٍ... الحديث». [متفق علیه].
Meaning:" you are going to a nation from the people of the scriptures (divine books – Jews and the Christians), invite them to testify that Laa'ilaahailla- Allah (i.e, there is no deity worthy of worship except Allah) and I am Allah's Messenger, and if they obey you to do so, then inform them that Allah has made it obligatory upon them to observe five salah(prayers) in every day and night…. To the end of the hadith". Reported by Imam Muslim, on the authority of Ibn Abbas.
It was also reported by Imam Albukhari and its wordings are;
«فَلْيَكُنْ أَوَّلُ مَا تَدْعُوهُمْ إِلَى أَنْ يُوَحِّدُوا اللَّهَ عَزَّ وَجَلَّ».
Meaning:” let (Islamic monotheism) be the first thing you will invite them to (i.e, testifying to the oneness of Allah).
And the explanation of that is also [contained] in the long hadith [popularly known as hadith Jibril] in which the Angel Gabriel asked the prophet (s.a.w) about the levels of religion: Islam, Iman and Ihsan, after that the prophet (S.A.W) said to his companions –as in the last part of the hadith-:
«هَذَا جِبْرِيلُ أَتَاكُمْ يُعَلِّمُكُمْ دِينَكُمْ».
Meaning: "this is (Jibril i.e, angel Gabriel. He came to you in order to teach you your religion."
So, the first obligatory thing to learn in religious matters is the lesson that is contained in the hadith of Jibril, and the first level of the [three] levels of the religion is Islam and the first pillar of Islam is Ash-shahadatani.