He saw a sick man. He had never seen anyone unwell before.
When he was 16 Siddhattha married a beautiful princess and they soon had a baby son. For a while he was happy with his wife and family and stayed inside the palace as his father had ordered.
Eventually Siddhattha became bored and wanted to know more of the world. One day, when he was 29 years old, he sneaked out of the palace while his father was not looking. While he was outside he saw 4 things that surprised and worried him. He thought about those things for a long time.
He saw an old man. He had never seen an old person before.