<p>4:7 <i>He again defines a certain day, a today, saying through David a long time afterwards (in the words already quoted): Today, if you shall hear His voice, harden not your hearts</i>- As explained on 3:6, that &quot;today&quot; is our today; in that right now at this moment, if we hear and believe His voice that promises us eternal inheritance in the Kingdom, we can be saved. We can be assured that if we die today or the Lord returns today, we shall be saved. By grace. This is the crucial importance of life and living today. And again we see the point made about Divine inspiration- God spoke through David in his Psalms. This emphasis upon inspiration was necessary because there were sectors within Judaism which denied the Divine inspiration of anything apart from the Pentateuch. The appeal to not harden hearts is of course alluding to Pharaoh and the Egyptians, who hardened their hearts and were confirmed in it by being hardened by God. The point is that the Israelites who left Egypt repeated the same attitude- they too hardened their hearts, they thought like Egyptians. Despite, like the Egyptians, having seen evidence of God's hand through the signs and wonders done. The Hebrew Christians were in the same position.</p>