Genesis 16:4-6 NIV
 He slept with Hagar, and she conceived. When she knew she was pregnant, she began to despise her mistress.  Then Sarai said to Abram, “You are responsible for the wrong I am suffering. I put my slave in your arms, and now that she knows she is pregnant, she despises me. May the Lord judge between you and me.”  “Your slave is in your hands ,” Abram said. “Do with her whatever you think best.” Then Sarai mistreated Hagar; so she fled from her.
It doesn't take long for the consequences of Abram and Sarai's sinful (and stupid) decisions to start surfacing. As often, the initial damage is relational. Hagar's pregnancy causes her to show deep disrespect, gross insensitivity and even contempt towards Sarai. She "...began to despise her mistress." (v. 4)
As a leader, I personally have been deeply saddened when someone, who used to serve with humility and honour, develops a prideful and rebellious arrogance towards towards those in authority over them. Often this follows a season of favour or promotion in their lives. They forget that often the promotion is actually because of their servant heart and is linked to the unique favour on the leader they are serving. They begin to develop an unhealthy sense of superiority, presumption and entitlement. Life rarely goes well for them after this.
So it is with Hagar. Her attitude towards Sarai becomes so intolerable and the tension between them becomes so great that eventually she runs away.
Sarai and Abram are far from without fault here. This whole thing was Sarai's master plan and Abram could have stopped it at any stage. She treats Hagar as an object to be used and abused and he abdicates all responsibility as head of the family, basically indicating that it's not his problem.
Simply, sin has consequences. Always. Without exception. These consequences affect those who commit the sin, but the ripple effect can be much wider. The fall out can last much longer. Families are damaged, communities affected, indeed nations may be impacted. The Arab-Israeli tensions we still see in present day were birthed with Ishmael and then Isaac.
While confession and repentance always lead to God's grace and forgiveness, the consequences often can't be erased. The Apostle Paul would later write: "Don’t be misled: No one makes a fool of God. What a person plants, he will harvest." (Gal 6:7 MSG)