Narrated [Ibn 'Umar (RA)]:

I said, "O Allah's Messenger (ﷺ) , I sell camels at al-Baqi'. I sell for Dinars and take Dirhams (for them), and sell for Dirhams, and take Dinars (for them), I take this for that and give that for this (i.e. Dinars and Dirhams)." Allah's Messenger (ﷺ) replied, "There is no harm in taking them at the current rate so long as you do not separate leaving something still to be settled (from the exchange)." [Reported by al-Khamsah and al-Hakim graded it Sahih (authentic)].

وَعَنْهُ قَالَ: { قُلْتُ: يَا رَسُولَ اَللَّهِ! إِنِّي أَبِيعُ بِالْبَقِيعِ, فَأَبِيعُ بِالدَّنَانِيرِ وَآخُذُ اَلدَّرَاهِمَ, وَأَبِيعُ بِالدَّرَاهِمِ وَآخُذُ اَلدَّنَانِيرَ, آخُذُ هَذَا مِنْ هَذِهِ وَأُعْطِي هَذَهِ مِنْ هَذِا? فَقَالَ رَسُولُ اَللَّهِ‏-صَلَّى اَللَّهُ عَلَيْهِ وَسَلَّمَ‏-: لَا بَأْسَ أَنْ تَأْخُذَهَا بِسِعْرِ يَوْمِهَا مَا لَمْ تَتَفَرَّقَا وَبَيْنَكُمَا شَيْءٌ } رَوَاهُ اَلْخَمْسَةُ, وَصَحَّحَهُ اَلْحَاكِمُ [1]‏ .‏