Passage
For if our heart reprehend us, God is greater than our heart and knoweth all things.
1 John 3:20 (DRB)
Nearby Context
1 John 3:18 My little children, let us not love in word nor in tongue, but in deed and in truth.
1 John 3:19 In this we know that we are of the truth and in his sight shall persuade our hearts.
1 John 3:20 For if our heart reprehend us, God is greater than our heart and knoweth all things.
1 John 3:21 Dearly beloved, if our heart do not reprehend us, we have confidence towards God.
1 John 3:22 And whatsoever we shall ask, we shall receive of him: because we keep his commandments and do those things which are pleasing in his sight.
Study Lenses
The verse centers on "all things", "heart", "reprehend", "greater", "than", and "knoweth". It is saying that the verse draws attention to "all things" and "heart", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 19's "In this we know that we are..." into verse 21's "Dearly beloved if our heart do not...", so "all things" and "heart" belong inside that flow. In 1 John context, the local focus is Christ, faith, and discipleship.
A plain takeaway is to answer the verse's own emphasis on "all things" and "heart" with trust shaped by these words, not by a vague optimism outside the passage.