"Have you not considered how Allah presents an example, [making] a good word [like] a good tree," which is 'La ilaha illa Allah' (There is no god but Allah). "Its root is firmly fixed" in the earth, "and its branches [high] in the sky," meaning: its crown, in which the fruit resides.
﴿أَلَمْ تَرَ كَيْفَ ضَرَبَ اللَّهُ مثلا كلمة طيبَة﴾ هِيَ لَا إِلَهَ إِلا اللَّهُ ﴿كشجرة طيبَة﴾ وَهِيَ النَّخْلَةُ؛ وَهِيَ مَثَلُ الْمَؤْمِنِ ﴿أَصْلهَا ثَابت﴾ فِي الأَرْضِ ﴿وَفَرْعُهَا فِي السَّمَاءِ﴾ أَيْ: رَأْسُهَا الَّذِي تَكُونُ فِيهِ الثَّمَرَة