Bulugh al-Maram
Also reported by Abu Da’ud mentioning the above addition without the words “the string is untied”, but both versions are weak.
وَهَذِهِ اَلزِّيَادَةُ فِي هَذَا اَلْحَدِيثِ عِنْدَ أَبِي دَاوُدَ مِنْ حَدِيثِ عَلِيٍّ دُونَ قَوْلِهِ: { اِسْتَطْلَقَ اَلْوِكَاءُ } وَفِي كِلَا الْإِسْنَادَيْنِ ضَعْف ٌ 1 .
Reference