722. hadíth
وَ نَهَى رَسُولُ اَللَّهِ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ: أَنْ يُتَخَطَّى اَلْقِطَارُ قِيلَ يَا رَسُولَ اَللَّهِ وَ لِمَ قَالَ «لِأَنَّهُ لَيْسَ مِنْ قِطَارٍ إِلاَّ وَ مَا بَيْنَ اَلْبَعِيرِ إِلَى اَلْبَعِيرِ شَيْطَانٌ ».
The Messenger of Allah (swt) (peace and blessings of Allah (swt) be upon him and his family) forbade stepping over the camel line (caravan). It was asked: "O Messenger of Allah (swt), why?" Prophet (saws) replied: "Because there is not a single camel line except that between one camel and the next there is a devil."