When they came to Marah, they could not drink of the waters of Marah, for they were bitter: therefore the name of it was called Marah. And the people murmured against Moses, saying, What shall we drink? And he cried unto the Lord; and the Lord showed him a tree, which when he had cast into the waters, the waters were made sweet.@Exodus 15:23–25
John Newton (1725–1807)

John Newton, Olney Hymns (London: W. Oliver, 1779), Book 1, number 13.

Windsor Christopher Tye, 1533; arranged in the Booke of Musicke, by William Daman, 1591 (🔊 pdf nwc).

Bitter, indeed, the waters are
Which in this desert flow;
Though to the eye they promise fair,
They taste of sin and woe.

Of pleasing draughts I once could dream,
But now, awake, I find,
That sin has poisoned every stream,
And left a curse behind.

But there’s a wonder-working wood,
I’ve heard believers say,
Can make these bitter waters good,
And take the curse away.

The virtues of this healing tree
Are known and prized by few;
Reveal this secret, Lord, to me,
That I may prize it too.

The cross on which the Savior died,
And conquered for His saints;
This is the tree, by faith applied,
Which sweetens all complaints.

Thousands have found the blest effect,
Nor longer mourn their lot;
While on His sorrows they reflect,
Their own are all forgot.

When they, by faith, behold the cross,
Tho’ many griefs they meet;
They draw again from every loss,
And find the bitter sweet.