It is narrated from Hazrat Nu'man bin Bashir (may Allah be pleased with him) that the Holy Prophet (peace and blessings be upon him) once said from the pulpit: "He who does not thank for a little, does not thank for much. He who does not thank people, does not thank Allah. Mentioning the blessings and favors of Allah is gratitude; neglecting them is ingratitude. Unity is mercy and division is punishment."
Hadith Referenceمسند احمد / أول مسند الكوفيين / 18449
Hadith Gradingحکم دارالسلام:قوله: من لم يشكر الناس لم يشكر الله ، صحيح لغيره، وهذا إسناد ضعيف، فيه أبو عبدالرحمن لم يعرف