When a person curses something, the curse ascends to heaven and the gates of heaven are closed against it. Then it descends to earth and its gates are closed against it. Then it turns right and left and when it finds no exit it returns to what was cursed if it deserves to be cursed; otherwise it rebounds to the one who uttered it
Authentic hadithعن أبي الدرداء رضي الله عنه مرفوعاً: «إن العبد إذا لعن شيئًا، صَعَدَتِ اللعنةُ إلى السماء، فَتُغْلَقُ أبوابُ السماء دونها، ثم تَهْبِطُ إلى الأرض، فَتُغْلَقُ أبوابُها دونها، ثم تأخذ يمينًا وشمالاً، فإذا لم تجد مَسَاغًا رجعت إلى الذي لُعِنَ، فإن كان أهلا لذلك، وإلا رجعت إلى قائِلها»
Abu Ad-Dardā' (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "When a person curses something, the curse ascends to heaven and the gates of heaven are closed against it. Then it descends to earth and its gates are closed against it. Then it turns right and left and when it finds no exit it returns to what was cursed if it deserves to be cursed; otherwise, it rebounds to the one who uttered it."
Explanation
If the slave of Allah curses something with his tongue, his curse ascends to the heavens, however the gates of the heavens are closed against it. Then it returns back to earth, and the gates of earth are also closed and it is not admitted therein. Then it turns right and left, and if it does not find a way or a place to settle in, it returns to the thing that was cursed if it deserves to be cursed; otherwise, it returns to and afflicts the one who uttered it.
Source · Narrated by Abu Daoud
From the Hadith Encyclopedia (hadeethenc.com).