قُلْ أَعُوذُ بِرَبِّ النَّاسِ مَلِكِ النَّاسِ إِلَهِ النَّاسِ
Say: I seek protection in the Lord of mankind; the King of mankind; the God of mankind."
[Surah al Naas 114]
These ayat in this Surah have not come with a "waw al-'atf" (i.e. the word "and") in between them so it is not permissible in origin to say, "In the Lord of mankind, and the King of mankind, and the God of mankind." It has only come as, "Say: I seek protection in the Lord of mankind; the King of mankind; the God of mankind."
This is so that it will not be suspected that there are three essences [dhat] because there is only One: Allah (subhanahu wa ta'ala) - the Lord, the King, the God. And so that it will not be suspected that what is intended is more than one, rather He (subhanahu wa ta'ala) is One. So Laa ilaaha illaa Allah [there is no god but Allah].
(Adapted from Lamsat Bayaniyyah fi Nusus min al-Tanzeel by Dr. Fadil Salih al-Samira'i)