Michael Carrick's men fell behind 1-0 in the first half after Lisandro Martinez turned the ball into his own net. United drew level before the interval when Bryan Mbeumo converted the equaliser to make it 1-1. The visitors' fortunes improved significantly after the break as Patrick Dorgu's strike completed the comeback, giving United a 2-1 advantage in the 50th minute.
In a thrilling contest, Arsenal thought they had rescued a point when Mikel Merino scored in the 84st minute. But there was one more twist as Matheus Cunha's brilliant goal clinched all three points for United in the 87th minute.
The result prompted jubilant celebrations from United both on the pitch and among their travelling fans, and it seems Amad has now carried those festivities onto social media.
Before kick-off, social media figure and Arsenal fan Jay had shared a post on X (formerly Twitter) predicting the outcome.
He wrote: "Arsenal are winning 4-0, they just sent me the script."
Amad didn't hesitate to serve a swift retort to the fan, quoting the initial prediction and pairing it with a snapshot of the final score. He cheekily posted: "Enjoy KID" accompanied by a winking emoji.
Jay retaliated with: "Buck me in ends g, don't tweet me ever again."
Yet Amad had the last word, delivering a final jab: "Your only hope is a corner (laughing emoji). Be humble KID (shushing emoji)."
This victory ensures United's unbeaten record under interim manager Carrick remains intact. The win also propels them above Chelsea in the Premier League table, securing a fourth-place position.
Arsenal, on the other hand, remain four points clear of both Manchester City and Aston Villa at the top. However, the loss meant they missed an opportunity to widen their lead.
United are set to return to the pitch on Sunday, hosting Fulham at Old Trafford (2pm kick-off), followed by a match against Tottenham the subsequent week.