"I heard 'Umar bin Al-Khattab say: 'The Messenger of Allah (ﷺ) said: "Exchanging gold for gold is usury unless it is done on the spot. (Exchanging) wheat for wheat is usury, unless it is done on the spot. (Exchanging) barley for barley is usury unless it is done on the spot. (Exchanging) dates for dates is usury, unless it is done on the spot."
Sunan Ibn Majah Book 12, Hadith 117
← Previous Hadith "When anyone of you buys a slave woman let him say: 'Allahumma inni as'aluka khairaha wa khaira ma jabaltaha alaihi, wa a'udhu bika min sharriha wa sharri ma jabaltaha alaihi (O Allah, I ask You for the goodness within her and the goodness that You have made her inclined towards, and I seek refuge with You from the evil within her and the evil that You have made her inclined towards).' And he should pray for blessing. And if anyone of you buys a camel then he should take hold of its hump and pray for. blessing and say similar words."

Sunan Ibn Majah Book 12, Hadith 116 Next Hadith → "Ubadah bin Samit and Mu'awiyah happened to meet, either in a church or in a synagogue. 'Ubadah bin Samit narrated to them and said: 'The Messenger of Allah (ﷺ) forbade us from selling silver for silver, gold for gold, wheat for wheat, barley for barley, and dates for dates.'I one of them said: "And salt for salt," but the other did not say it. "And he commanded us to sell wheat for barley, or barley for wheat, hand-to-hand, however we wished."

Sunan Ibn Majah Book 12, Hadith 118