Umar bin al-Khattab (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "O Umar, you are a strong man; do not harm the weak. When you want to touch the Black Stone, if the place is clear, touch it; otherwise face it and say the takbir."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9261