In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Ibnul Qayyim [rahimahullaah] said:
Ikhlaas and Tawheed are a tree in the heart; its branches are the [good] deeds and its fruits is the good life in this world and everlasting bliss in the afterlife. And just as the fruits of Jannah are neither cut off [by change of season] nor are they out of reach, likewise this is the case with the fruits of Tawheed and Ikhlaas. Shirk, lies and Riyaa are a tree in the heart; its fruits – in the worldly life- are fear and anxiety, grief and distress in the soul and oppression against the heart. Its fruits in the afterlife are the tree of Zaqqoom and an everlasting punishment. And Allaah has mentioned these two trees in Surah Ibraaheem:
أَلَمۡ تَرَ كَيۡفَ ضَرَبَ ٱللَّهُ مَثَلاً۬ كَلِمَةً۬ طَيِّبَةً۬ كَشَجَرَةٍ۬ طَيِّبَةٍ أَصۡلُهَا ثَابِتٌ۬ وَفَرۡعُهَا فِى ٱلسَّمَآءِ
تُؤۡتِىٓ أُڪُلَهَا كُلَّ حِينِۭ بِإِذۡنِ رَبِّهَاۗ وَيَضۡرِبُ ٱللَّهُ ٱلۡأَمۡثَالَ لِلنَّاسِ لَعَلَّهُمۡ يَتَذَڪَّرُونَ
وَمَثَلُ كَلِمَةٍ خَبِيثَةٍ۬ كَشَجَرَةٍ خَبِيثَةٍ ٱجۡتُثَّتۡ مِن فَوۡقِ ٱلۡأَرۡضِ مَا لَهَا مِن قَرَارٍ۬
See you not how Allaah sets forth a parable? A goodly word as a goodly tree, whose root is firmly fixed, and its branches (reach) to the sky (i.e. very high). Giving its fruits at all times, by the Leave of its Lord, and Allaah sets forth parables for mankind in order that they may remember. And the parable of an evil word is that of an evil tree uprooted from the surface of earth, having no stability. [Surah Ibraaheem. Aayaat 24-26]
[Source: Al-Fawaa’id. Pages 239-240]