The Scofield Bible Commentary, by Cyrus Ingerson Scofield, [1917], at sacred-texts.com
Surely
Kadesh-barnea is, by the unbelief of Israel there, and the divine comment on that unbelief (Num 14:22-38); (Deu 1:19-40); (Co1 10:1-5); (Heb 3:12-19) invested with immense spiritual significance. The people had faith to sprinkle the blood of atonement (Exo 12:28) and to come out of Egypt (the world), but had not faith to enter their Canaan rest. Therefore, though redeemed, they were a forty years' grief to Jehovah. The spiritual application is made in (Heb 6:3-11):
(See Scofield) - (Heb 6:4).