Hadith 8:1865
Abu Bakr narrated to us, he said: Ibn Numayr narrated to us, from Abdullah, from Nafi’, from Ibn Umar: That he used to ascend Al-Safa, face the House (the Kaaba), then say "Allahu Akbar" (God is the Greatest) three times. Then he would say: "There is no god but Allah alone, He has no partner; to Him belongs the dominion, and to Him belongs the praise, and He is capable of all things." He would raise his voice with that, then supplicate for a little while, then supplicate for a little while. Then he would do that at Al-Marwa until he had done that seven times. Thus, the Takbir (saying "Allahu Akbar") would be twenty-one times. He would barely finish until it would become difficult for us, even though we were young men.
حدثنا أبو بكر قال حدثنا بن نمير عن عبد الله عن نافع عن بن عمر أنه كان صعد على الصفا استقبل البيت ثم كبر ثلاثا ثم قال لا إله إلا الله وحده لا شريك له له الملك وله الحمد وهو على كل شيء قدير يرفع بها صوته ثم يدعو قليلا ثم يدعو قليلا ثم يفعل ذلك على المروة حتى يفعل ذلك سبع مرات فيكون التكبير واحدا وعشرين تكبيرة فما يكاد يفرغ حتى يشق علينا ونحن شباب