Doubt, doubtful, doubtfulness: We must be very careful to not let these words creep into our hearts to shake our faith in the word of God. We cannot believe some words of God and doubt other words of God!
Jesus is very clear when he says: “It is written, that man shall not live by bread alone, but by every word of God” (Luke 4:4). “Heaven and earth shall pass away, but my words shall not pass away” (Matthew 24:35).
“Forever, O LORD, thy word is settled in heaven” (Psalm 119:89).