“He that hath received his testimony hath set to his seal that God is true.”  
John 3:33

On the earth, people bare witness of events, at times events that happened to others, but more often, events in their lives- they notice the causes and the results and at times they use those witnesses as a yardstick for their expectations in life.
For example, a man who has observed that every time it rains he eventually gets admitted to the hospital, would begin to use the rainfall as a yardstick for his health.
The Bible says:
“If we receive the witness of men, the witness of God is greater…”  1John 5:9
If you can hear someone’s witness and believe it, then you can hear God’s witness and believe it and God’s witness is greater- absolutely effective.
Jesus is the express image of God, and the main verse states if you receive his witness you have decided in your life that God is true, so listen to this witness:
“Consider the ravens: for they neither sow nor reap; which neither have storehouse nor barn; and God feedeth them: how much more are ye better than the fowls? Consider the lilies how they grow: they toil not, they spin not; and yet I say unto you, that Solomon in all his glory was not arrayed like one of these. If then God so clothe the grass, which is to day in the field, and to morrow is cast into the oven; how much more will he clothe you…” Luke 12:24,27-28