For the longest time, lava has been a resource in Minecraft that griefers use to burn down the world, or players use it for smelting the resources they have mined. Regardless of your uses for lava, the problem has always been that it has always been a finite resource. Eventually, you would run out and need to go looking for a lava pool again. Fortunately, that has all changed with the first Cliffs and Caves update in Minecraft, bringing with it a whole new way to turn lava into a renewable resource. Here is how to do it.
To make an infinite source of lava, you need to acquire Pointed Dripstone and a Cauldron. Unfortunately, before the second part of Cliffs and Caves comes out, the only way to do this in a Survival world is to trade with a Wandering Trader, but if you are okay with Creative, you can do that as well.
To start, find a location that you want to place your cauldron. Above that needs to be your Pointed Dripstone hanging from a non-flammable block. Make sure all blocks in the surrounding area are safe from catching on fire. Now place a lava source block above the block that the Pointed Dripstone is hanging from.
With the above in place, your Pointed Dripstone will slowly drip lava into the cauldron below. As time goes by, it will eventually fill with lava while not taking anything away from the lava block above. So, while the process to fill the cauldron will be slow, you will have a completely renewable and reusable source of lava at the tips of your fingers.