"Geh Kiang" is Singlish (local Singapore colloquial language) for smarty-pants or smart aleck. We pretend we can do something well when we do not actually know how to, and we mess up.
Spiritually, we can be "geh kiang" before God too. Instead of trusting, waiting on, and obeying Him, we take things into our own hands. Oftentimes, though there may be some apparent success initially, it ends up with nothing but pain and misery. The Bible says we will reap what we sow. The Bible says that there is a way that seems right unto man, but the end of it are the ways of death.
The story of Sarah and Hagar also reminds us of the futility of legalism or self-righteousness. It is better to trust God for His promise in the gospel and be saved.
