Arabic text
عن أنس رضي الله عنه قال: كُنَّا عِنْدَ عُمَرَ فَقَالَ: «نُهِينَا عَنِ التَّكَلُّفِ».
Translation
Anas (may Allah be pleased with him) reported: We were with ‘Umar, and he said: "We were forbidden from the affectation."
Explanation
‘Umar (may Allah be pleased with him) informs that the Messenger of Allah (may Allah's peace and blessings be upon him) forbade them from needlessly putting themselves into hardship, whether in words or deeds.
Source: HadeethEnc.com