He explained thus: the owner of the horse simply gives some water to it for drinking, some grass and hey for eating and a simple shelter made of four sticks stuck to the ground with a roof for staying. Just by getting these simple things, the horse obeys all the commands of the owner. He carries the owner to where ever he needs to go along with his heavy luggages.
In the past, the horses were used in the battle fields to fight against the enemies. The horses could see that the enemies have sharp swords, arrows and spears, still they would risk their lives to take the owner to the middle of the enemies just because the owner provides them with those simple things.
Allah mentions in this surah "Verily, man is ungrateful to his Lord" (100:6). Why? Because, Allah doesn't give humans to eat grass, rather He gives them three different plates of food to eat at three different meals. For breakfast one dish, for lunch another dish and yet another for dinner. For drinking, Allah doesn't give us dirty water, rather pure water and besides that, juice, cool drinks…etc. For a shelter, Allah doesn't give us something that is made up of four sticks stuck to the ground, rather a house where there is heat in the winter and air condition or fans in the summer. Even then, we don't follow our Allah, as much as a horse follows his owner.
What is the reason? The love of the wealth of this world. What are we going to do about it? We have to stay away from these wealth for some time regularly and start giving the excess away for the cause of Allah.