Uyaynah bin Abd al-Rahman (may Allah have mercy on him) narrates from his father that Buraydah (may Allah be pleased with him) said: I was walking along and saw the Prophet (peace and blessings be upon him), and I thought that he (peace and blessings be upon him) had some need. So at times I would come in front of him (peace and blessings be upon him) and at times I would keep back, until he (peace and blessings be upon him) called me and took hold of my hand. He (peace and blessings be upon him) saw a man who was bowing and prostrating a great deal. He (peace and blessings be upon him) said: "Do you think he is showing off? Do you think he is showing off?" Then he (peace and blessings be upon him) let go of my hand and said: "Adopt moderation, adopt moderation." Then he (peace and blessings be upon him) struck one of his hands on the other and said: "Whoever is harsh in this religion, it will overcome him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4742