Ecclesiastes 2:7; Ecclesiastes 7:21; Ecclesiastes 10:7

7 I bought male and female slaves and I had homeborn slaves. Also I possessed flocks and herds larger than all who preceded me in Jerusalem.
21 Also, do not take seriously all words which are spoken, so that you will not hear your servant cursing you.
7 I have seen slaves riding on horses and princes walking like slaves on the land.