Sunan an-Nasa'i 4589
It was narrated that Ibn 'Umar said:
"I came to the Prophet and said: 'Wait, I want to ask you something. I sell camels in Al-Baqi with a price set in Dinars but I accept Dirhams instead.' He said: 'There is nothing wrong with it if you take the price on that day, still unfinished business between you both (buyer and seller)"'
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ عَمَّارٍ، قَالَ حَدَّثَنَا الْمُعَافَى، عَنْ حَمَّادِ بْنِ سَلَمَةَ، عَنْ سِمَاكِ بْنِ حَرْبٍ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عُمَرَ، قَالَ أَتَيْتُ النَّبِيَّ صلى الله عليه وسلم فَقُلْتُ رُوَيْدَكَ أَسْأَلُكَ إِنِّي أَبِيعُ الإِبِلَ بِالْبَقِيعِ بِالدَّنَانِيرِ وَآخُذُ الدَّرَاهِمَ ‏.‏ قَالَ ‏
"‏ لاَ بَأْسَ أَنْ تَأْخُذَ بِسِعْرِ يَوْمِهَا مَا لَمْ تَفْتَرِقَا وَبَيْنَكُمَا شَىْءٌ ‏"‏ ‏.‏