In Arabic, the meaning of the first part of the Shahadah is:

لَا مَعْبُودَ بِحَقٍّ إِلَّا الله

There is none worthy of worship in truth except Allah.

 If anything other than Allah is worshipped then it is false:

Allah the Exalted said:

ذلِكَ بِأَنَّ اللَّهَ هُوَ الْحَقُّ وَأَنَّ مَا يَدْعُونَ مِن دُونِهِ هُوَ الْبَـاطِلُ وَأَنَّ اللَّهَ هُوَ الْعَلِىُّ الْكَبِيرُ

{That is because Allah is the Truth, and that which they call upon other than Him is falsehood, and because Allah is the Most High, the Great}

[al-Hajj (22): 62]

And He the Exalted said:

فَاعْلَمْ أَنَّهُ لاَ إِلَـهَ إِلأاللَّهُ

{Know! there is none worthy of worship except Allah…}

[Muhammad (47): 19]

Muhammad b. ‘Abd al-Wahhab al-Wasabi al-‘Abdali, al-Qawl al-Mufid fi Adillat al-Tawhid, (San’a: Maktabat al-Irshad, 1427/2006), 27.