vs.4 Even before a word is oon my tongue, behold, O LORD, You know it altogether
God knows everything. This isn't a new consept for most of us. This passage here is talking about how much God knows us. He knows because we are His creations and the very work of His hands.
If your hobby was building cars, don't you think you would know the cars you build inside, and out? You would know every nut and bolt of your car. It is the same with God. He knows us cause he created us.
This passage goes a step beyond that. In verse four is talks about how God knows what we are going to say even before we are going to say it. Why? Because he made the brain to have a thought. He made a language to carry that thought to others. And He made the tongue to audibly express, with language, that thought.
What a great God we serve that knows us, knows what we're going through every minet of the day, and guids us in His perfect will. What a great God!