Al-Matalib al-'Aliyah 492 — Humility (khushu)

It is narrated from Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "When one of you is praying and feels in his stomach a sound, a rumbling from the movement of wind, or something like that (giving the sense that his ablution has been broken), let him place his hand on his nose (giving the impression of a nosebleed, to avoid embarrassment and for the sake of concealment), and break off the prayer and go out."
The chain of this narration contains a narrator named Ishaq bin Abi Farwah, who is da'if (weak) and matruk (abandoned) according to the hadith scholars, because of which this chain is technically weak; however, the jurists have considered such an action commendable for the sake of modesty and concealment.