Thus have I heard. […]
“I shall show you, monks, the Teaching’s similitude to a raft: as having the purpose of crossing over, not the purpose of being clung to. Listen, monks, and heed well what I shall say” — “Yes, Lord,” replied the monks. and the Blessed One spoke thus:
“Suppose, monks, there is a man journeying on a road and he sees a vast expanse of water of which this shore is perilous and fearful, while the other shore is safe and free from danger. But there is no boat for crossing nor is there a bridge for going over from this side to the other. So the man thinks: ‘This is a vast expanse of water; and this shore is perilous and fearful, but the other shore is safe and free from danger. There is, however, no boat here for crossing, nor a bridge for going over from this side to the other. Suppose I gather reeds, sticks, branches and foliage, and bind them into a raft.’ Now that man collects reeds, sticks, branches and foliage, and binds them into a raft. Carried by that raft, laboring with hands and feet, he safely crosses over to the other shore. Having crossed and arrived at the other shore, he thinks: ‘This raft, indeed, has been very helpful to me. Carried by it, laboring with hands and feet, I got safely across to the other shore. Should I not lift this raft on my head or put it on my shoulders, and go where I like?’
“What do you think about it, O monks? Will this man by acting thus, do what should be done with a raft?” — “No, Lord” — “How then, monks, would he be doing what ought to be done with a raft? Here, monks, having got across and arrived at the other shore, the man thinks: ‘This raft, indeed, has been very helpful to me. Carried by it, and laboring with hands and feet, I got safely across to the other shore. Should I not pull it up now to the dry land or let it float in the water, and then go as I please?’ By acting thus, monks, would that man do what should be done with a raft.
“In the same way, monks, have I shown to you the Teaching’s similitude to a raft: as having the purpose of crossing over, not the purpose of being clung to.
From Majjhima Nikāya (MN) 22 Alagaddupama Sutta –
The Snake Simile (translated from the Pali by Nyanaponika Thera)