When the water at Marah was bitter, Moses had to cast a tree into the water stream to sweeten the water or make it drinkable.
The words: Bitter and Better both start with a B and end with Tter. The only difference is: the letter I and E.
Bitter has the focus on I, me, myself, flesh.
Better has the focus on God: exalting Him, endurance,
When we take the focus of self and turn it to God, our life turns from Bitter to Better....
An interesting fact about the Moringa Tree:
’The ’Moringa oleifera’. This tree has been used successfully to cleanse turbid waters from the River Nile and other areas.
We cannot be dogmatic in saying that the moringa was the tree the Israelites used to purify the waters of Marah. The Bible does not give us enough information about either the tree or the water. (Marah means “bitterness” by the way, which is why they named that place Marah).
It is also not certain whether the miracle was in God’s revealing to Moses the type of tree that would solve the problem, or in God’s producing a one-off miracle using a tree at the campsite. But the wording that says “the Lord shewed him [Moses] a tree” seems to be saying the solution was in a tree that was already growing in the area.
In any case, we do know that the moringa has remarkable properties — especially for rapidly purifying undrinkable water. So if we want to know, “Is there a tree that can quickly purify undrinkable water?”, the answer is clearly Yes. “Can the tree grow in that area?” Again the answer seems to be Yes.’
Source: http://creationtips.com/bitter_sweet_water.html