'Sure' in the Bible

But whoever habitually keeps His word and obeys His precepts [and treasures His message in its entirety], in him the love of God has truly been perfected [it is completed and has reached maturity]. By this we know [for certain] that we are in Him:

If you know that He is absolutely righteous, you know [for certain] that everyone who practices righteousness [doing what is right and conforming to God’s will] has been born of Him.

This is the [remarkable degree of] confidence which we [as believers are entitled to] have before Him: that if we ask anything according to His will, [that is, consistent with His plan and purpose] He hears us.