The passage is ambiguous as to which group of three were involved in this particular expedition to slake David's thirst
Was it the first three group: Adino/Eleazar/Shammah (v8-12)
Or was it the second three (v18-24) i.e. Abishai/Benaiah/Asahel
It almost seems that the Spirit/God would have us speculate as to which of the three groups were responsible
They both seem very capable of the great deed
Perhaps the design here is to take our eyes away from the instrument and think about the One who gave them the strength and courage so to do
Suffice for these men to know that God knows and that there will be no such ambiguity/speculation in that great Day when God will reward them and identify them as good/faithful servants

The story itself is pretty easy to follow and without much ado, we will turn to it and glean 4 main points from the passage:

1) THE CAUSE OF GOD WAS HOLED UP IN A CAVE/ADULLUM:

A/ Cause/God at this time was centred around David

[i] He is distinctly called God's anointed (v2) i.e. Christ (Greek)
No man/Bible (apart from Christ) was ever Prophet/Priest and King…but David was both Prophet and King (v2)
The godly/Israel would have been most supportive of David at this time.
What mourning over his sins…but nevertheless what love and loyalty they would have shown him.

[ii] David's importance is further seen when they nearly lost him in battle (18:3) and forbade him to fight again, saying:
Thou shalt not go forth: for if we flee away, they will not care for us; neither if half of us die, will they care for us: but now thou art worth ten thousand of us: therefore now it is better that thou succour us out of the city.
Not insignificant: Bride/Song saw her Beloved (Christ) as the fairest/ten thousand (5:10)

[iii] One/Christ's titles: "Son of David" NT's opening line:
The book/the generation of Jesus Christ, the son of David…

Not wrong to identify the whole cause/God around one individual.

B/ Furthermore, in this OT era with its outward significance's, Bethlehem was the place to be also
David's birthplace and more significantly…Christ's birthplace also
But thou, Bethlehem Ephratah, though thou be little among the thousands of Judah, yet out of thee shall he come forth unto me that is to be ruler in Israel; whose goings forth have been from of old, from everlasting. (Micah 5:2)
But the COI weren't in Bethlehem … a whole garrison/Philistines were there instead (v14) and David/men were holed up in Adullum
This cave doesn't enjoy a good press in the Bible: 1:22:1
While we can draw lovely Bible lessons from this earlier scene… yet you can't spend all your spiritual experience in a cave
There is a time to move on and to go from strength/strength
David was glad to get out of it… but now he's back again

C/ Certainly not good days for the cause/God
[i] The enemy: in the ascendancy - the work/God so restricted

[ii] Unsure as to what chronological order these things happened
Supposing they happened as related/Bible…then here we have the Philistines still a formable force even after a series/defeats

[iii] That's Christian life for you - one hard bloody battle after another - and the enemy often in the stronger position

2) SUCH A SITUATION SERVED TO  INCREASE DAVID'S DESIRE FOR THE PURE WATER OF BETHLEHEM:

A/ David had evidently tasted this water before
Probable…seeing he was born there
A rich gospel application:
When we are born into God's family (John 1:13/3:3-7)
We drink of the water of life (John 4:14/Rev 22:17)
We leave our water pots (love/world) behind (John 4:28) and we "drink at that fountain life giving and free" (McCheyne)
We don't stop drinking

B/ David did not forget about this water, even in the deepest distress, nor did he lose his taste for it
Indeed (titled this 2nd point) the dire situation he found himself in only heightened his desire for it
This all instructive:

[i] Never abandon or relegate the gospel when in times/trial
You will find your sweetest comfort there
Let the time/affliction but serve to drive you to Christ
Thirst after him the more cp. Psalm 42:1-3
You will find Him to be the sweeter
Cold water always tastes better in hotter climates

[ii] Enjoy the water while you have the freest access to it
The enemy can move in and deny it to you
Here was something which sustained David in his hour/need
He thought most favourably of this well of sweet water and his expression of its sweetness led to great heroics for the faith

C/ It is wrong to think: I will not miss what I have never had
Can't live in near spiritual bankruptcy so that you will never miss your Bible/prayer and spiritual experiences if taken from you
That would be perpetual life in a dark, thirsty cave
Life in permanent defeat with no motivation to fight

D/ Try and capture the experiences of the saints/old whose knowledge/Christ was very deep.
 Samuel Rutherford:
O Christ, He is the fountain…the deep sweet well of Love
The streams of earth I've tasted, the more I'll drink above
There to an ocean's fulness - His mercy doth expand
And glory, glory dwelleth in Immanuel's Land

3) DAVID HAD MEN WHO WERE WILLING TO RISK LIFE AND LIMB TO MAKE THIS WATER AVAILABLE:

A/ David himself could not go
Perhaps age was against him (v1) or the restrictions of 18:3
But nevertheless, so great was his passion and his desire for this water - 3 men were willing to risk life/limb to get it for him
Speak passionately re: Christ and your passion will spread/others
You'll put backbone into men
These boys had fled with David. Felt themselves to be on the back foot again/again by the Philistines

B/ David's request was not considered to be trivial or to be mistimed or in any way unreasonable
Can only be because of the spiritual implications

[i] Water stood for all that was of God esp. of a basic kind
[ii] David was so loved because he is a picture/type of Christ
[iii] Or (David) stood for every spiritual believer

C/ Something needed to be done and 3 men volunteered
Were not asked (as such) far less sent…but they went

[i] They saw the tremendous good that would flow from success
The King glorified (They are known as "David's mighty men")
A fellow Believer would be encouraged and revived
The well/Bethlehem would soon be out of the enemies' hands
(Not necessarily here/now - but a solid contribution was made)
Soon - anyone would be able to drink of this well  - located at "the gate"

[ii] Think of those who risked all to bring us the gospel
 Church history is full of martyrs and heroes who loved not their lives unto death  (Revelation 12:11) but hacked their way through the fiercest/enemies so that we could have free access/Bible
What we owe these folk cannot be measured
We owe it to the next generation to fight ourselves, if not to actually get the water  - at least to keep the well accessible

D/ The enemy was prepared to fight to keep these men away
(Just as Shammah fought to keep them from the lentils: v12)
The enemy will always fight to keep you from spiritual things
You've got to risk all to keep your soul healthy/well

4) SUCH A WILLINGNESS WILL BE BROUGHT TO GOD'S FAVOURABLE NOTICE:

A/ Having successfully fought through a whole host (outnumbered) these men brought David his desired drink

B/ David didn't drink it - even though probably gasping - but poured it out unto the Lord as a drink offering (v16-17) very conscious of the tremendous price that was paid to get it
By so pouring it our as a drink offering before God, David ensured that this deed would be held in memorial before God
What a great reward they will get/Heaven
Likewise you if you contend so earnestly/faith as they did

C/ No one actually died (but could have) to get him the water - but One died to get you the water/Life even Jesus Christ