Not sure that this is right, but it’s a start. Comments would be appreciated.
A (19) The beauty of Israel is slain upon thy high places: how are the mighty fallen!
B (20) Tell it not in Gath, publish it not in the streets of Askelon; lest the daughters of the Philistines rejoice, lest the daughters of the uncircumcised triumph.
C (21-22a) Ye mountains of Gilboa, let there be no dew, neither let there be rain, upon you, nor fields of offerings: for there the shield of the mighty is vilely cast away, the shield of Saul, as though he had not been anointed with oil. From the blood of the slain, from the fat of the mighty,
D (22b) the bow of Jonathan turned not back,
D’ (22c) and the sword of Saul returned not empty.
C’ (23) Saul and Jonathan were lovely and pleasant in their lives, and in their death they were not divided: they were swifter than eagles, they were stronger than lions.
B’ (24) Ye daughters of Israel, weep over Saul, who clothed you in scarlet, with other delights, who put on ornaments of gold upon your apparel.
A’ (25-27) How are the mighty fallen in the midst of the battle! O Jonathan, thou wast slain in thine high places. I am distressed for thee, my brother Jonathan: very pleasant hast thou been unto me: thy love to me was wonderful, passing the love of women. How are the mighty fallen, and the weapons of war perished!
Not only are C and C’ connected by their common reference to valour/strength/might, but also the language of both sections echoes Psalm 133. The Psalm is short so I will post it here as it may help to see the links.
‘A Song of degrees of David. Behold, how good and how PLEASANT it is for brethren to DWELL TOGETHER IN UNITY! It is like the precious OINTMENT upon the head, that ran down upon the beard, even Aaron’s beard: that went down to the skirts of his garments; As the DEW of Hermon, and as the dew that descended upon the mountains of Zion: for there Yahweh commanded the blessing, even life for evermore.’
Here in the chiasm in C you have the words ‘dew’ and ‘oil’. In C’ David calls Saul and Jonathan ‘pleasant’ and ‘not divided’ which connects very strongly with the opening line of the Psalm – ‘Behold, how good and how pleasant it is for brethren to dwell together in unity!’.
The Psalm tells us that this spiritual unity is like the dew and oil. In C’ Saul and Jonathan are united in death as well as life. However in C the lack of dew and oil seems to contradict this unity.
In 1 Samuel 31:6 we read – ‘So Saul died, and his three sons, and his armourbearer, and all his men, that same day together.’ This word ‘together’ is the same word as occurs in the Psalm – ‘together in unity’.
So we realise that there is a distinction here in David’s lament between the act of death (or final act of life) and when a person is dead and can’t be anything. When David laments, Saul and Jonathan are dead and so, in C, there is no oil or dew. But in C’ the reference to ‘death’ describes their final act of life, looking back to when they were united in battle against the enemies of God.
In fact, this chiasm centres on that very act – Saul and Jonathan died, united, fighting for God.