Sunan Abu Dawud - سنن أبي داود
23. Commercial Transactions (Kitab Al-Buyu) - كتاب البيوع
14) Chapter: Regarding Paying With Gold For A Price In Silver
The tradition mentioned above has also been transmitted by Simak (b. Harb) with a different chain of narrators and to the same effect. The first version is more perfect. It does not mention the words "at the current rate".
14) باب فِي اقْتِضَاءِ الذَّهَبِ مِنَ الْوَرِقِ
حَدَّثَنَا حُسَيْنُ بْنُ الأَسْوَدِ، حَدَّثَنَا عُبَيْدُ اللَّهِ، أَخْبَرَنَا إِسْرَائِيلُ، عَنْ سِمَاكٍ، بِإِسْنَادِهِ وَمَعْنَاهُ وَالأَوَّلُ أَتَمُّ لَمْ يَذْكُرْ . " بِسِعْرِ يَوْمِهَا "