There are three testimonies:

–      The first is: (Allah witnesses that there is no deity except Him,) Allah is the One who created heavens and earth, controls death and life, runs seas and rivers … etc. There isn’t and won’t be any other deity to defy Him. Moreover, such testimony is an auto-testimony: the testimony by the Almighty that there is no deity except Him.

{ وَكَفَىٰ بِاللَّهِ شَهِيدًا}

(and sufficient is Allah as Witness.) (An-Nisaa: 79)

–      The second is: (and [so do] the angels) which is a testimony by the witness. The Almighty told the angels to be obedient, and so were they.

–      The third one is (and those of knowledge) which is a testimony of evidence. Allah (swt) says:

{ إِنَّ فِي خَلْقِ السَّمَاوَاتِ وَالْأَرْضِ وَاخْتِلَافِ اللَّيْلِ وَالنَّهَارِ لَآيَاتٍ لِّأُولِي الْأَلْبَابِ}

(Indeed, in the creation of the heavens and the earth and the alternation of the night and the day are signs for those of understanding.) (Aal-Imran: 190)

Thus, you witness that there is no deity by Allah by virtue of the evidences Allah has created.

{ وَآيَةٌ لَّهُمُ الْأَرْضُ الْمَيْتَةُ أَحْيَيْنَاهَا وَأَخْرَجْنَا مِنْهَا حَبًّا فَمِنْهُ يَأْكُلُونَ}

(And a sign for them is the dead earth. We have brought it to life and brought forth from it grain, and from it they eat.) (Yaseen: 33)

{ وَآيَةٌ لَّهُمُ اللَّيْلُ نَسْلَخُ مِنْهُ النَّهَارَ فَإِذَا هُم مُّظْلِمُونَ}

(And a sign for them is the night. We remove from it [the light of] day, so they are [left] in darkness.) (Yaseen: 37)

There are many crystal-clear signs in the universe, sun, moon, rivers, ourselves, life, death, … etc. that guide us to the Sole Creator.

In everything there is a sign,

Indicating that the Lord is but One,

The above verse is among the greatest ones which elevates people of knowledge immediately behind angels and prophets. This is because we come to know the existence of Allah by means of knowledge. Moreover, Islam is a religion of knowledge and never accepts ignorance and backwardness. Islam aims to lead humanity as such, despite the fact that we are backward in a so-long decline.

(… قَائِمًا بِالْقِسْطِ …) (…that He is] maintaining [creation] in justice): Why it’s ‘He is’ not ‘they are’? Because Allah maintains justice without the need to have it testified neither by angels nor by those of knowledge. Yet, you need a testimony to realize His presence. Likewise, the angels need a testimony of the witnesses to His existence; but He is the only one who testifies that He, Himself, maintains the creation in justice.

( لَا إِلَٰهَ إِلَّا هُوَ الْعَزِيزُ الْحَكِيمُ … ) (…There is no deity except Him, the Exalted in Might, the Wise.): These are two attributes of the Almighty, who maintains the creation in justice while He is exalted in Might; can do without the worship of His creatures; and makes everything with wisdom.