Hebrews 12:18-25. Chiastic structure copied from Chiastic Analysis of the Epistle to the Hebrews,  arranged by John Bligh (Athenaeum Press, Heythrop College, Oxon, England: 1966). Bligh's work is almost entirely in Greek. For website purposes, I have used unaccented Greek from the Unbound Bible, Nestle-Aland 26, at unbound.biola.edu
I have added English from the New American Standard Bible, revised.

A 18 ou gar proselhluqate yhlafwmenw 
For you have not come to a mountain that can be touched 
B kai kekaumenw puri kai gnofw kai zofw kai quellh
and to a blazing fire, and to darkness and gloom and whirlwind,

19 kai salpiggoV hcw kai fwnh rhmatwn 
and to the blast of a trumpet and the sound of words 
C hV oi akousanteV parhthsanto 
which sound was such that those who heard begged 
D mh prosteqhnai autoiV logon
that no further word be spoken to them.
C* 20 ouk eferon gar to diastellomenon 
For they could not bear the command, 
B* kan qhrion qigh tou orouV liqobolhqhsetai
"If even a beast touches the mountain, it will be stoned."
A* 21 kai outw foberon hn to fantazomenon 
And so terrible was the sight, 
a mwushV eipen 
that Moses said, 
A ekfoboV eimi kai entromoV
"I am full of fear and trembling."
W 22 alla proselhluqate siwn orei 
But you have come to Mount Zion 
X kai polei qeou zwntoV 
and to the city of the living God, 
Y ierousalhm epouraniw 
the heavenly Jerusalem, 
Z kai muriasin aggelwn panhgurei
and to myriads of angels,
Z* 23 kai ekklhsia prwtotokwn 
to the general assembly and church of the firstborn
Y* apogegrammenwn en ouranoiV 
 who are enrolled in heaven, 
X* kai krith qew pantwn 
and to God, the Judge of all, 
W* kai pneumasi dikaiwn teteleiwmenwn
and to the spirits of the righteous made perfect,
A* 24 kai diaqhkhV neaV mesith 
and to ...the mediator of a new covenant, 
a* ihsou ...Jesus, 
A kai aimati rantismou kreitton lalounti para ton abel
and to the sprinkled blood, which speaks better than the blood of Abel.
B 25 blepete mh paraithshsqe ton lalounta 
See to it that you do not refuse Him who is speaking. 
C ei gar ekeinoi ouk exefugon 
For if those did not escape 
B* epi ghV paraithsamenoi ton crhmatizonta 
when they refused him who warned them on earth, 
A* polu mallon hmeiV oi ton ap ouranwn apostrefomenoi
much less will we escape who turn away from Him who warns from heaven.

Verse 25 is also in the next chiasm.