It is narrated from Hazrat Anas (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: This religion is very serious and firm, therefore include gentleness in it.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 13052
Hadith Gradingحکم دارالسلام:حسن بشواهده، وهذا إسناد ضعيف لضعف عمرو بن حمزة