Mark 14:6
And Jesus said, Let her alone; why trouble ye her? she hath wrought a good work on me.
Cross-reference
Matthew 26:10
Parallel
Matthew 26:10 is the parallel account — Jesus defends her beautiful act with nearly identical words.
John 12:7
Parallel
John 12:7 records the same event with Jesus saying 'Leave her alone' and linking the anointing to his burial — deepening the meaning here.
2 Kings 4:27
Allusion
In 2 Kings 4:27, Elisha's command 'Leave her alone' protects a distressed woman — here Jesus uses the same phrase to defend the woman's act of devotion.