Sunan an-Nasai 19061
In-book no 4325أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، وَعَبْدِ اللَّهِ بْنِ دِينَارٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَجُلاً، قَالَ يَا رَسُولَ اللَّهِ مَا تَرَى فِي الضَّبِّ قَالَ " لَسْتُ بِآكِلِهِ وَلاَ مُحَرِّمِهِ " .
It was narrated from Ibn 'Umar that a man said: "O Messenger of Allah what do you think about mastigures?" He said: "I do not eat them but I do not say that they arte Haram."