Nasai

Hadith Commentary:
This sale is not permissible, because in the sale of currency (sarf), mutual possession (taqabud) in the same sitting is necessary, as has already been mentioned in the Book of Transactions (Kitab al-Buyu‘). At the end of the hadith, the narrator is uncertain whether the word used was "season" (mawsim) or "Hajj." The relevance to the chapter heading is derived from the fact that the Messenger of Allah (sallallahu alayhi wa sallam) arrived in Madinah.

Hadith Commentary:
➊
That is, Sufyan, when narrating, sometimes would not specify the term of the credit, and at other times he would mention the term of the credit, such as until the season or until Hajj, he would set a period for the credit.

➋
In any case, such a transaction is not permissible, because in the buying and selling of currency, credit is not allowed; rather, the transaction must be completed in the same sitting, as this issue has been explained in the Book of Sales (Kitab al-Buyu‘).

➌
In this hadith, the arrival of the Messenger of Allah (sallallahu alayhi wa sallam) in Madinah is mentioned; therefore, Imam Bukhari (rahimahullah) has narrated this hadith.

And Allah knows best.

Hadith Commentary:

For example, if one person gives cash rupees and the other says, "I will give the equivalent rupees after one month," then this is not permissible. In the transaction of currency exchange (bay‘ al-sarf), it is a condition according to all scholars that both exchanged items must be handed over on the spot (taqabud), and it is not valid with a delay. Now, there is a difference of opinion regarding whether, if the commodity is the same—for example, rupees for rupees or gold coins for gold coins—an increase or decrease is permissible or not. According to the Hanafis, when the commodity is the same, any increase or decrease is not permissible, and according to their school, exchanging old and new coins becomes difficult. It is better to add some coins of another type so that increase and decrease become permissible according to all.

(Wahidi)

From the generality of this hadith, Imam Bukhari rahimahullah has deduced that trading on land is permissible.

Hadith Commentary:
(1)
Imam Bukhari rahimahullah has established, from the generality of the noble verse and the hadith, the permissibility of engaging in trade on land and elsewhere. Thus, Hazrat Bara’ bin Azib and Hazrat Zayd bin Arqam radi Allahu anhuma said:
We were engaged in the profession of trade during the time of the Messenger of Allah sallallahu alayhi wa sallam.
From these words, Imam Bukhari rahimahullah has substantiated his point.

(2)
The mutual exchange of gold and silver coins is called "sarf" (currency exchange).
There are two forms of this:
• Silver for silver, and gold for gold.
For its permissibility, two conditions must be met:
• The weight of both must be equal.
• It must be hand to hand (immediate exchange).
If on one side it is cash and on the other side deferred, or if in the case of cash there is any increase or decrease in weight, then the transaction becomes haram.
• Purchasing gold in exchange for silver, or silver in exchange for gold.
In this case, equality in weight is not necessary; however, it is necessary that the exchange be hand to hand (immediate).
If the transaction is deferred along with any increase or decrease, then it will not be permissible.
We will explain its details further ahead; however, Imam Bukhari rahimahullah has established from the generality of this hadith the permissibility of trade on land.
And Allah knows best.

Hadith Commentary: Benefits and Issues: The intention of Abu Minhal’s partner was that if the mutual exchange of gold and silver in the form of credit were not permissible, then the people of the marketplace would have objected to it. Their not objecting is evidence of its permissibility. However, this incident also proves that if the people of the marketplace, despite being aware, do not object, then this is not necessarily evidence of permissibility; the reason could be something else as well.

The exchange of gold and silver refers to giving gold in return for silver and taking silver in return for gold. In other words, it means taking dirhams in exchange for dinars or dinars in exchange for dirhams. The fundamental point is that the mutual ratio between gold and silver keeps fluctuating, and their value keeps changing; therefore, immediate (spot) exchange is permissible, but deferred exchange is not permissible because it is possible that by the time of payment, the value may change, which could then lead to the possibility of dispute.