Trade is permissible. [9] In other situations, trade can also be obligatory, impermissible, allowed, or disliked. Examples of trade being obligatory are a guardian selling an orphan’s property if it becomes essential to do so or a judge selling a bankrupt person’s assets according to the [correct] prerequisites. Examples of trade being impermissible are selling carrion, blood, or pork. Examples of trade being allowed is selling food when prices are high and so on. Regarding trade that is disliked, some gave the example of transactions made with individuals who have mostly impermissible wealth. See Al-Umm by Shafi`i (3/3); Sharh al-Zurqani `ala Mukhtasar Khalil wa Hashiyat al-Banani (5/4); Al-Fawakih al-Dawani by al-Nafrawi (2/72); Mughni al-Muhtaj by al-Shirbini (2/39); and Nihayat al-Muhtaj by al-Ramli (3/477).

Evidences:

Firstly: From the Book [10] Translator’s note: i.e., the Qur’an. 
The Statement of Allah Exalted, “Allah has permitted trading.” [11] al-Baqarah, 275.
The Statement of Allah Exalted, “Call upon witnesses when a deal is finalized.” [12] al-Baqarah, 282.
And the Statement of Allah Exalted, “Rather trade by mutual consent.” [13] al-Nisa’, 29.
In these verses, Allah Exalted permits trade by mutual consent, which is a term that features in trade agreements (including buying and selling). [14] See Al-Umm by Shafi`i (3/3) and Ahkam al-Qur’an by Ibn al-Faras al-Andalusi (2/517).

Secondly: From the Sunnah
1. The statement of the Prophet after he had specified usurious types of transactions, “If the items are different, then trade as you wish, so long as it is hand-to-hand.” [15] Related by Muslim (1583).
2. Hakim ibn Hizam narrated, “The Messenger of Allah said, ‘Both parties in a transaction have a choice so long as they have not separated. (Or, he said: ‘…until they separate.’) If they both speak the truth and make things clear, their transaction will be blessed for them, but if they conceal and lie, the blessing of their transaction will be erased.’” [16] Reported by Muslim (1532).

Thirdly: From the scholarly consensus
A consensus on this issue has been transmitted by al-Mawardi, [17] Mawardi said: “As for scholarly consensus, it is apparent amongst them all without exception, even if they differed on its manner and description, to the extent that even the leading Companions expressed the view and allowed it for themselves.” Al-Hawi (5/5). Ibn Qudamah, [18] Ibn Qudamah said: “Trade is permissible according to the Book, the Sunnah, and scholarly consensus, and all Muslims agree upon its permissibility.” Al-Mughni (3/480). al-Nawawi, [19] Nawawi said: “As for the ruling the author mentioned, which is the permissibility of trade, it is one of the things proven by the Book, the Sunnah, and scholarly consensus.” Al-Majmu` (9/148). al-Zayla`i, [20] Zayla`i said: “Its permissibility is established in the Book, the Sunnah, and scholarly consensus. [In the Book, Allah Exalted says:] ‘Allah has permitted trading and forbidden interest’ (al-Baqarah, 275). As for the Sunnah, it is related that the Prophet g once sold a saddle blanket and a drinking bowl, and the people also traded and he approved of that. And as for scholarly consensus, the scholars have agreed upon its permissibility.” Tabyin al-Haqa’iq (4/3). Ibn Hajar, [21] Ibn Hajar said: “The Muslims agree on the permissibility of trade.” Fath al-Bari (4/287). al-`Ayni, [22] `Ayni said: “The proof of its permissibility is the Book…and the consensus of the scholars, for they are united regarding the permissibility of trade.” Al-Binayah Sharh Al-Hidayah (8/3). Ibn al-Humam, [23] Ibn al-Humam said: “The legitimacy of trade is found in the Book, as per the Statement of Allah Exalted, ‘Allah has permitted trading’ (al-Baqarah, 275); in the Sunnah, as per the statement of the Prophet g, ‘O assembly of traders, this trading involves swearing oaths and lying, so dilute your trading with charity’; and in the scholarly consensus, which is united upon its permissibility.” Fath al-Qadir (6/247). and al-Hattab. [24] Hattab said: “The scholarly consensus is completely agreed upon its permissibility.” Mawahib al-Jalil (6/11).