Explain the reason for the appearance of elastic forces during deformation?

Elastic force arises from deformation. The reason is the interaction of body molecules. At short distances, molecules repel, and at large distances, they attract. Without deformation, there is no elastic force. When compressed, the elastic force tends to straighten the body, that is, the molecules begin to repel each other. When stretching, to compress the body, since a large distance is formed between the molecules and they are rapidly attracted to each other.