Humbert arrived for the contest without his racquets, apologising at the ball toss.
The Frenchman was soon provided with his essential equipment to a round of applause from the crowd but still took some time to get going on Court 2, losing the opener.
Humbert weathered that setback, though, and replied in impressive fashion, emerging a 3-6 6-2 7-5 6-4 winner for his third consecutive victory against top-10 opponents on grass.
"I love to play on grass. I have played a lot of good matches," Humbert said.
"I think about the match last year against [Nick[ Kyrgios. It was a big battle. I won Halle, so I think I play very nice [on grass] because of my serve, and my backhand is very great."
He added: "It is a big victory. [Ruud] played very well the last few years, so I am very happy."