The book of Reveletions calls satan the ancient serpent or serpent of old. Just like in the garden of Eden where he tempted Adam and Eve is the same way he tempts us. There are moments when God speaks and even proves his word true but situations will cause us to doubt. If you've ever reached a moment where you begin to question yourself if God really spoke to you inspite of God's powerful manifestation in the beginning, then it is automatically the wisper of the devil. Remember what he told Eve." Did God really say you should not eat of that tree?" God speaks once. Any other views will be from satan. Psalms 62:11 says, once God has spoken twice have I heard that all power belongs to him.When God speaks, it doesn't mean everything will be smooth.Temptations and afflictions will come but our faith and patience will help us obtain his promises. (Hebrews 6:12). Remember the Israelites when they asked Moses whether there were no graves in Egypt that he should take them to the wilderness to suffer. Inspite of all the signs and wonders that God had done through Moses?