Certainty is at the heart of the Lord's Good News message. He leaves His People in no doubt. Knowing equals certainty - and vice versa!
Here's a truly awesome example:
"... this is the testimony that
God has given us eternal life,
and this life is in His Son.
He who has the Son has life;
he who does not have the Son of God does not have life," 1 John 5'11-12.
And here's another:
"... knowing this, that our old man (old nature) was crucified with Him, that the body of sin might be done away with, that we should no longer be slaves of sin," Romans 6'6.
And yet another:
"And whatever you do, do it heartily,
knowing that from the Lord
you will receive the reward of the inheritance;
for you serve the Lord Christ," Colossians 3'23-24.
Praise the Lord for the wonderful assurance of the word of Christ.