Why is a contract necessary in all economics activities like selling and renting?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

There is no doubt that making a contract constitutes one of the necessities of life. The contract is an agreement between two parties who, according to such an agreement, have agreed upon carrying out the terms, conditions and items stated in the agreement concerning some activity such as selling, renting and so on.
Such an agreement becomes necessary since no one can live alone or without need of others. In addition, it is not only wrong but also impossible for one to be in no need of others, especially selling, purchasing, renting, etc…
This case, in turn, necessitates making contracts and agreements so that everyone can benefit from the others or deal with them. Thus, the contracts become the natural channel and normal means by which we can achieve our goals or organize and govern our socio-economic activities.
Allah knows best.