Can Christians fall into serious sin?

The Bible acknowledges that even true believers can fall into serious sin, as seen in the case of David, who was described as a man after God's own heart yet committed grave offenses. This reality underscores the fallen nature of humanity and the continuous need for God's grace. David's experience shows that regardless of the depth of one's sin, the path back to God is available through sincere repentance and reliance on His mercy, as articulated in Psalm 51. This truth serves to remind Christians that they must always remain vigilant and dependent on God's grace to sustain them, recognizing that their righteousness is rooted not in their own efforts but in Christ's atoning work.