Quran 18:14

وَرَبَطۡنَا عَلَىٰ قُلُوبِهِمۡ إِذۡ قَامُواْ فَقَالُواْ رَبُّنَا رَبُّ ٱلسَّمَـٰوَٲتِ وَٱلۡأَرۡضِ لَن نَّدۡعُوَاْ مِن دُونِهِۦۤ إِلَـٰهً۬ا‌ۖ لَّقَدۡ قُلۡنَآ إِذً۬ا شَطَطًا ١٤

We strengthened their hearts when they stood up and proclaimed: "Our only Lord is the Lord of the Heavens and the Earth. We will never worship any other god beside Him. Otherwise, we would be far astray.