Read the breed's reaction honestly
An Arabian experiences fireworks night at higher volume than most breeds, and not only in his ears. Arabians are sensitive, quick-thinking horses that react first and assess later, bond closely to their people and their companions, and take emotional cues from both. That reactivity is manageable, but plan for the horse you actually have: a fit, sharp Arabian who spins at a flapping tarpaulin in daylight will not sleep peacefully through a display, and a horse that panics in a stable can rear, scramble and injure himself against the walls. The aim of the evening is not to make him enjoy fireworks; it is to surround him with so much normality that the bangs never become the biggest thing happening.
Spend the energy earlier in the day
Ride or work him during the day, finishing well before dark, so he comes into the evening physically ready to rest rather than fresh and electric. Turn him out for his normal hours if that is his routine. What not to do is exercise him at dusk to tire him out at the last minute: a hot, wound-up Arabian led in as the first rockets go up starts the night at his worst. A horse that has worked, eaten and settled into his evening rhythm by the time the noise starts has a far better chance of staying under his threshold.
Set the stable up as a refuge
Stable him next to the calmest horse on the yard, ideally the companion he already trusts, because an Arabian takes a neighbour's behaviour as evidence about whether to panic. Give him a deep bed with banks, plenty of hay to work through, water checked and topped up, and the lights on so flashes read as changes in brightness rather than explosions out of darkness. Put a radio on at a steady level. Remove anything loose in the box he could knock over or tangle in if he does spin, check the door bolts, and keep his rug, if he wears one, correctly fitted with sound straps.
Your presence is the calming tool
With this breed, the most effective calming aid is you. Arabians watch their people closely, and an owner who appears calm, speaks in an ordinary voice and does ordinary things sends the strongest available signal that the world is not ending. Visit through the evening, groom him if that is something he enjoys, and then simply be around: sitting nearby with a book calms more horses than anxious fussing, which tells a perceptive horse that you are frightened too. If he is sweating, trembling and hurting himself despite everything, call your vet for advice rather than struggling on alone.
After the last bang, and extra eyes just in case
When the displays end, check him over for cuts and heat in the legs, offer water, and walk him in hand around the yard if he has settled. Check fencing and gates before any turnout the next morning, because a horse that leaned on a fence at midnight may have left it ready to fail at dawn. And before the evening starts, it is worth letting your KinsLe Circle of Love neighbours know fireworks are expected near your yard, so the local network of pet lovers around you is already half-watching, and if your Arabian ever does get loose in the dark there are people nearby who know whose horse he is.