"God" (Heb 1:1) "in these last days has spoken to us in His Son" (:2). "After it was at the first spoken through the Lord, it was confirmed to us by those who heard" (2:3). It is "what we have heard" (:1). "For this reason we must pay much closer attention to what we have heard" (:1). "We must pay more careful attention therefore" (:1 NIV). It was "the word spoken through angels" (:2) and "are they not . . . sent out to render service for the sake of those who will inherit salvation?" (1:14). It was salvation "spoken through the Lord, [and] it was confirmed to us" (2:3). "Therefore we ought to give the more earnest heed to the things which we have heard' (:2 KJV). What was heard? It was the Gospel. But we must be careful "that we do not drift away from it" (:2 NIV) which is "what we have heard" (:2). We can forget if we are careless and ignore it. The author therefore says to them "it is hard to explain, since you have become dull of hearing" (5:11). The process is illustrated by drifting away which is being swept along by a water current or washed away. The Gospel can be seen as a boat dock which you grab on to for safety, security and to have the truth. But if you're not attentive you can lose your handhold and drift away. Worse yet you can refuse to accept it and deliberately push off from the dock back into the current. Rejecting it represents unbelief. "Therefore do not throw away your confidence" (10:35). Prolonging that process results in apostasy because that person has neglected to "pay more careful attention" (2:2 NIV) or "pay much closer attention" (:2 NASB). The Gospel represents "the things which we have heard [and not] at any time . . . should [we] let them slip" (:2 KJV). It represents salvation and heaven to the believer.