Sayyiduna Abu Sa'id al-Khudri (may Allah be pleased with him) narrates this as a marfu' hadith: The Prophet (peace and blessings be upon him) said: "Sometimes a man says a word by which he intends no harm, his aim being only to make people laugh with it, yet because of that word he falls (into the depths of Hell) a distance greater than that of the sky."
This narration was recorded by Imam Ahmad, and its chain contains a narrator, Abu Isra'il Isma'il bin Khalifah, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الأدب / 13149
Hadith Gradingمحدثین:إسنادہ ضعیف
Hadith Takhrij«اخرجه احمد فى المسند (38/3) ، أخرجه مسند أحمد برقم: 10938»