The Bible says in Matthew 21:5+7-9:
"Tell the people on Mount Zion, “Your king is coming to you. He does not come proudly, riding on a donkey, on the foal of a donkey.”
They brought the donkey and the colt and placed their cloaks on them for Jesus to sit on."

Donkeys are known for their ability to carry heavy loads. They demonstrate great endurance and stability. They can carry loads up to their own body weight.
During the time Jesus lived on earth, they were often used as pack animals.