Buddha: "Monks! I am going to teach you Dhamma comparing it with a boat, it's aim is to cross not to cling to it. Listen and give your attention I'm now speaking about it."
Monks: "As you wish Lord!"
Buddha: Suppose that a man is traveling on a road. On his journey, a great river comes. Being on this side of the bank of that river was very dangerous while another bank of that river was very safe. But, to reach from here to there neither there was a boat nor there was a bridge. Then the man thinks - 'Here is a great river! Remaining on this side of this river is full of danger while reaching the other side is safe, but to reach that other side here is neither a boat nor a bridge. What if I collect these grasses, woods, and substances like this and make a boat and by the effort of my own hands and feet I drive that boat and reach to that other side.' Thus after thinking this that man began to collect grasses and woods and combining all these he created a boat and with the help of that boat driving that boat with the effort of his hands and feet he reached the other side of that great river. After reaching the other side of that river he might think -" This boat has become very useful to me. With the help of this boat and driving it with my efforts of hands and feet I have reached this side of this river. Why not I carry this boat in my back or in my head and walk?" If he did this, did that man do that thing which should be done?
Monks: No Lord!
Buddha: What should that man do to that boat? That man after reaching the other side of the river might think - "This boat has become very useful to me. With the help of this boat and driving it with my efforts of hands and feet I have reached this side of this river. Why not I leave this boat in this dry land or make this boat float in its own way in the river itself and go wherever I want?" Doing this he does that thing which should be done to that boat. In this way monks, I have taught you Dhamma like this boat, its aim is to reach the other side not to cling in it! After understanding the Dhamma like a boat, one should ultimately leave the Dhamma itself, what to talk of the Adhammas!
Alagaduppama Sutta Tripitaka
This conversation between monks and lord Budhha is taken from Alagaduppama Sutta of the Tripitaka. This teaching of Buddha is very revolutionary in nature. Generally, we see that even in some useful paths people finally start to cling to the path itself. They develop prejudice towards the path they practice and might develop a mindset that considers that path as the superior path. Some might consider their path worth clinging to it. But lord Buddha here shatters all these mindsets and makes it clear to monks that whichever thing you cling to it's itself bondage in itself. Dhamma is just like a boat to reach the other side (Nirvana), after reaching another side one should leave clinging to the Dhamma itself also!