The Quran says:

By the snorting, panting horses, striking sparks of fire with their hooves, as they gallop to make raids at dawn, and raising clouds of dust, forcing their way into the midst of the enemy, surely, man is ungrateful to his Lord. He himself bears witness to that. Surely, he is ardent in his love of wealth. Is he not aware of the time when the contents of the graves will be brought out? And the hearts’ contents shall be brought into the open? Surely, on that Day, they will know that their Lord had full knowledge of them all.( 100:1-11)

The horse is an extremely faithful animal. It sacrifices itself to the uttermost for its master, even at the cost of its life.

It expresses symbolically what man should be like, i.e. that he should have faith in his Lord, just as the horse trusts its master. But in practice this does not happen.

In this world an animal is grateful to its master, but man is not grateful to his Lord. Here an animal recognises its dues to its master, but man does not do so in regard to his Lord. Here an animal is engaged devotedly in serving its master. But this is not the case with man.

Man, values only that animal which is faithful to him. Then how can he fail to understand that only those will have value and importance in the eyes of God (in the Hereafter) who have proved themselves His faithful servants? It is a sad fact that love of money turns people blind, so that they fail to understand a reality already experienced in their immediate surroundings.

This state of affairs is not going to last. Death must come, reminding man that he is totally in the grip of God. Death, in actual fact, is an entrance to the next world of reckoning. There man has to appear before a divine court, where no human act is hidden from the divine eye.

Source: The Quran for All Humanity