John Gill Commentary Hebrews 2:1

"Therefore we ought to give the more earnest heed to the things that were heard, lest haply we drift away [from them]." — Hebrews 2:1 (ASV)

Therefore we ought to give the more earnest heed
This is an inference from the apostle's discourse in the preceding chapter; since he, by whom God has spoken in these last days, is his Son, who is infinitely above the angels, they being his creatures, and worshippers of him, and ministers to him, and his; therefore the greater regard should be had to the Gospel spoken by him:

even to the things which we have heard; which are no other than the truths of the Gospel, which had been preached to them, and which were heard by the apostles, who preached them to them; and they had heard them from the apostles, or from Christ himself, and were what their forefathers had desired to hear, and which the carnal ear has not heard; for there is an internal and an external hearing of the Gospel.

Now the hearers of it should give heed, or attend to it, to beware of that which is pernicious and hurtful, and to regard that which is good and profitable; and this giving heed includes a close consideration of Gospel truths, a diligent inquiry into them, a high esteem for them, a strict adherence to them, and a watchfulness to retain what is heard, and to conform to it:

and this was to be done "more earnestly" than their forefathers or they themselves had; or this may be put for the superlative degree, signifying that they should give the most earnest heed; for they had the most abundant reason to give heed, since what they heard was not from Moses, and the prophets, to whom they did well to take heed, but from Christ the Son of God, who was greater than they:

"lest at any time we should let them slip": and this either refers to persons; and so the Vulgate Latin version renders it, "lest we should run out"; and the Syriac version, "lest we should fall"; and the Arabic version, "lest we should fall from honesty": which may intend partial slips and falls, to which the people of God are subject; and which are often owing to inadvertency to the word; for the Gospel, when duly attended to, is a preservative from falling:

or it may refer to things, even the doctrines of the Gospel, lest we should let them slip out of us, through us, or besides us: the metaphor seems to be taken either from leaking vessels, which let out what is put into them, or from strainers which let the liquor through, and it falls on the ground, cannot be gathered up, and so becomes useless; which is expressive of unprofitable hearing of the word, through inattention, negligence, and forgetfulness, and the irrecoverability of it, when it is gone: the Gospel may be lost to some that hear it, as to any real benefit and advantage by it; and some who hear the Gospel may be lost and perish; but the grace of the Gospel can never be lost.