The Belzer Rebbe refused to use the Esrog, as it wasn't intended for him!

Rabbi Meir Stein, recounted regarding the purchase of an Esrog for the Rebbe Shalom Eliezer Halberstam of Ratzfert son of the heilige Divrei Chaim of Sanz. When the Esrog merchant arrived in Budapest with his few Esrogim, he decided that he would sell the most beautiful Esrog to the heilige Rabbi Shalom Eliezer of Ratzfert. When the heilige Rebbe of Ratzfert heard this, he traveled to Budapest in order to buy the Esrog. However, when he arrived there, the merchant requested no less than twelve thousand good and solid florins Rhenish. The heilige Rebbe of Ratzfert turned to him and said: "I will give no more than ten thousand florins!" But the merchant was undeterred and held firm to his price. Seeing this, the Rebbe of Ratzfert immediately left the place.

Shortly thereafter, several Belzer Chassidim came in to the merchant and asked him how much he was requesting for the Esrog. He answered them: twelve thousand florins. The Chassidim immediately paid the twelve thousand florins and purchased the Esrog for Rebbe Aharon of Belz.

When the Ratzferter Rebbe saw this, he immediately sent two messengers (one of whom was the Rabbi David Yehoshua Gross) to the Belzer Rav, and instructed them to tell the Rebbe that this falls under the Rabbinic halachic principle of עני המהפך בחררה ובא אחר ונטלו "A poor man seeking a cake, and another came and took it" (Shulchan Aruch Choshen Mishpat, Chapter 237, Paragraph 1).

Lo and behold, as soon as the messengers of the Ratzferter Rebbe entered the Belzer Rav's room, and before they could even say anything, the Belzer Rav immediately took the Esrog and gave it to the messengers of the Rebbe of Ratzfert without saying a single word. And it was wondrous, as everyone clearly saw the Ruach Hakodesh of the Belzer Rav. It wasn't intended for him!