The example of someone who delays [repenting] is like someone who wants to uproot a tree, but finds that it’s very strong and will only be uprooted with difficulty.
So he said: I will delay its uprooting for one year, then I will come to uproot it.
But he doesn’t know the longer the tree lives, the more firmly rooted it’ll be, and that the older he is, the weaker he’ll be.
Source: Mukhtasar Minhaj al-Qasideen by Imam Ibn Qudamah (pp. 251-267)
