Preface: The fundamental ruling on transactions is that they are permissible

The fundamental ruling on transactions is that they are permissible, and they can only be made unlawful by a prohibition transmitted in the Shariah. [1507] Shafi`i said: “The fundamental principle regarding all trades is that they are permissible when conducted with the mutual consent of the parties involved and when the commodities being sold are lawful, except for what the Messenger of Allah g forbade. Anything falling under the meaning of what the Messenger of Allah g forbade is impermissible. Anything beyond this, we consider permissible based on the declaration of the permissibility of trade in the Book of Allah Exalted that we have described.” Al-Umm (3/3). See also Tafsir al-Qurtubi (3/356), Majmu` al-Fatawa by Ibn Taymiyyah (29/133), Kashf al-Asrar by al-`Ala’ al-Din al-Bukhari (4/360), I`lam al-Muqi`in by Ibn al-Qayyim (1/259), Al-Qawa`id by Ibn Rajab, p. 340, and Al-Ashbah wa al-Naza’ir by Ibn al-Mulaqqin (1/111).

Evidence:
(1) From the Book:
The Statement of Allah Exalted: “Allah has permitted trading and forbidden interest.” [1508] al-Baqarah, 275.
His Statement, “Allah has permitted trading”, implies that all trade is permissible. [1509] Tafsir al-Razi (7/78).
The Statement of Allah Exalted: “O believers! Do not devour one another’s wealth illegally, but rather trade by mutual consent.” [1510] al-Nisa’, 29.
Allah makes only mutual consent a prerequisite of trade. Therefore, if the mutual consent of the two parties to a contract is present, then the permissibility of that trade is established by the evidence of the Qur’an, except for things that are specifically forbidden by Allah and His Messenger. [1511] Al-Qawa`id al-Nuraniyyah by Ibn Taymiyyah, p. 280.
The general verses which command honouring all obligations and pledges like the Statements of Allah Exalted, “O believers! Honour your obligations”, [1512] al-Ma’idah, 1. “Honour your pledges”, [1513] al-Isra’, 34. “?the believers are also? those who are true to their trusts and covenants”, [1514] al-Mu’minun, 8. and “the righteous are… those who keep the pledges they make” [1515] al-Baqarah, 177. . [1516] Al-Qawa`id al-Nuraniyyah by Ibn Taymiyyah, pp. 265, 266.
In the following discussions, examples of permissible transactions will be mentioned.