There are7 condition that must be took in consideration during selling process; an agreement between 2 sane adults on a known specific lawful object owned by the seller, and the buyer should have access to it.

Conditions: The following conditions must be met for the sale to be valid

 1. There must be agreement between the seller and the buyer.

God says

Believers, do not devour each other’s wealth illegally, unless it be through trade which you conduct by mutual consent

4: 29

Abu Sa'id al-Khudri reports that the Prophet said

A sale can only be through mutual agreement

Related by Ibn Majah, hadith No. 2,185; Ibn Hibban, hadi th No. 4,967; al-Bayhaqi, vol. 6, p. 17.

2. Each of the two parties should be a person of age, sane and rational.

3. The seller must be the owner of what is being sold, or someone acting for the owner, such as an attorney, guardian, executor, manager or employee assigned to selling. No person may sell something he does not own.

The Prophet said to Hakim ibn Hizam

Do not sell what you do not possess

Related by Ahmad, hadith No. 15,311; Abu Dawud, hadith No. 3,503; al-Tirmidhi, hadith No. 1,232; al-Nassa’i, hadith No. 4,613; Ibn Majah, hadith No. 2,187.

4-What is being sold should be something that is permissible to use in the normal way, not in case of necessity.

Jabir reports that the Prophet said

God has forbidden the sale of wines, carrion, pigs and idols 

Related by al-Bukhari, hadith No. 2,236; Muslim, hadith No. 1,581.

Ibn 'Abbas reports that the Prophet said

If God forbids people to eat something, He also forbids them to take its price

Related by Ahmad, hadith No. 2,221; Abu Dawud, hadith No. 3,488; al-Bayhaqi in Al-Sunan al-Kubra, hadith No. 11,051.

5-What is being sold can be delivered to the buyer. What cannot be delivered is considered like something that does not exist, and as such it cannot be sold. It is in fact a form of gharar, which means something deceptive: it has an appearance but its substance is unknown. In such a sale, the buyer may give the price agreed but may not obtain what he bought. Thus, it is not permissible to buy a fish that is still in the water, the stones that are still in the dates, birds flying in the sky, milk still in the cow, the unborn cub, or an animal in the wild.

Abu Hurayrah reports

God’s messenger has forbidden any gharar sale

Related by Muslim, hadith No. 1,513.

6-The subject of the sale must be known to both parties, either both seeing it at the time of the sale or by describing it in a way that distinguishes it from other things. Lack of knowledge of what is being bought and sold counts as gharar, which is forbidden. To buy something one has not seen, or one has seen but does not know, and it is not present at the time of the deal is wrong.

7-What is being sold should be defined and the price should be clearly stated.