The Pharisees asked Jesus whether it was permissible to divorce, and He explained why Moses allowed for divorce, that it was because of their hardness of heart, and He continued,

“But from the beginning of the creation, God ‘made them male and female.’ ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh’; so then they are no longer two, but one flesh. Therefore what God has joined together, let not man separate” (Mark 10:6–9).

Perhaps you have heard that last part quoted by preachers in weddings, and now you know the background to that quote, that Jesus showed in the beginning, found in the first two chapters of Genesis, God made one man and one woman, intending that they remain as one until one of them dies.

Jesus will state one exception in Mark 10:11, 12, but His general rule stands, that once we marry, He intends for it to be for life.
Therefore, be wise in whom you decide to marry, and be sure to be the kind of person to whom someone would want to remain married.