Therefore we ought to give the more earnest heed to the things which we have heard, lest at any time we should let them slip. Therefore - Because God has spoken to us by his Son; and because that Son is so great and glorious a personage; and because the subject which is addressed to us is of such infinite importance to our welfare.
We ought to give the more earnest heed - We should hear the doctrine of Christ with care, candour, and deep concern.
Lest at any time we should let them slip - Μη ποτε παραρῥυωμεν· "Lest at any time we should leak out." This is a metaphor taken from unstanch vessels; the staves not being close together, the fluid put into them leaks through the chinks and crevices. Superficial hearers lose the benefit of the word preached, as the unseasoned vessel does its fluid; nor can any one hear to the saving of his soul, unless he give most earnest heed, which he will not do unless he consider the dignity of the speaker, the importance of the subject, and the absolute necessity of the salvation of his soul. St. Chrysostom renders it μη ποτε απολωμεθα, εκπεσωμεν, lest we perish, lest we fall away.