Hebrews 3:19

καὶ βλέπομεν ὅτι οὐκ ἠδυνήθησαν εἰσελθεῖν δι' ἀπιστίαν
So we see that they could not enter in because of unbelief.
Word Reference
Original Word Definitions
καὶ
G2532 CONJ
kai
and, also, even, so then, too, etc.; often used in connection (or composition) with other particles or small words
  • and, also, even, indeed, but
βλέπομεν
G991 V-PAI-1P
blepō
to look at (literally or figuratively)
  • to see, discern, of the bodily eye
    • with the bodily eye: to be possessed of sight, have the power of seeing
      • "perceive by the use of the eyes: to see, look descry"to turn the eyes to anything: to look at, look upon, gaze at"to perceive by the senses, to feel"to discover by use, to know by experience
    metaphorically to see with the mind's eye
    • to have (the power of) understanding
      • "to discern mentally, observe, perceive, discover, understand"to turn the thoughts or direct the mind to a thing, to consider, contemplate, to look at, to weigh carefully, examine
    in a geographical sense of places, mountains, buildings, etc. turning towards any quarter, as it were, facing it
ὅτι
G3754 CONJ
hoti
demonstrative, that (sometimes redundant); causative, because
  • that, because, since
οὐκ
G3756 PRT-N
ou
the absolute negative (compare G3361) adverb; no or not
  • no, not
ἠδυνήθησαν
G1410 V-AOI-3P
dynamai
to be able or possible
  • to be able, have power whether by virtue of one's own ability and resources, or of a state of mind, or through favorable circumstances, or by permission of law or custom
    • "to be able to do something"to be capable, strong and powerful
εἰσελθεῖν
G1525 V-2AAN
eiserchomai
to enter (literally or figuratively)
  • to go out or come in: to enter
    • of men or animals, as into a house or a city
      • "of Satan taking possession of the body of a person"of things: as food, that enters into the eater's mouth
    metaphorically
    • of entrance into any condition, state of things, society, employment
      • to arise, come into existence, begin to be
        • "of men, to come before the public"to come into life
      of thoughts that come into the mind
δι'
G1223
dia
through (in very wide applications, local, causal, or occasional)
  • through
    • of place
      • with
        • "in
      of time
      • throughout
        • "during
      of means
      • by
        • "by the means of
    through
    • the ground or reason by which something is or is not done
      • by reason of
        • "on account of"because of for this reason"therefore"on this account
ἀπιστίαν
G570 N-ASF
apistia
faithlessness, i.e., (negatively) disbelief (lack of Christian faith), or (positively) unfaithfulness (disobedience)
  • unfaithfulness, faithless
    • "want of faith, unbelief"weakness of faith

καὶ βλέπομεν ὅτι οὐκ ἠδυνήθησαν εἰσελθεῖν δι' ἀπιστίαν
19
So we see that they could not enter in because of unbelief.
Cross References

Jude 1:5

Ὑπομνῆσαι δὲ ὑμᾶς βούλομαι εἰδότας ὑμᾶς ἅπαξ τοῦτο ὅτι ὁ Κύριος λαὸν ἐκ γῆς Αἰγύπτου σώσας τὸ δεύτερον τοὺς μὴ πιστεύσαντας ἀπώλεσεν
5
I will therefore put in remembrance, you though ye once knew this, how that the Lord, having saved the people out of the land of Egypt, afterward destroyed them that believed not.

John 3:36

ὁ πιστεύων εἰς τὸν υἱὸν ἔχει ζωὴν αἰώνιον· ὁ δὲ ἀπειθῶν τῷ υἱῷ οὐκ ὄψεται ζωήν ἀλλ' ἡ ὀργὴ τοῦ θεοῦ μένει ἐπ' αὐτόν
36
He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.

Mark 16:16

ὁ πιστεύσας καὶ βαπτισθεὶς σωθήσεται ὁ δὲ ἀπιστήσας κατακριθήσεται
16
He that believeth and is baptized shall be saved; but he that believeth not shall be damned.

John 3:18

ὁ πιστεύων εἰς αὐτὸν οὐ κρίνεται· ὁ δὲ μὴ πιστεύων ἤδη κέκριται ὅτι μὴ πεπίστευκεν εἰς τὸ ὄνομα τοῦ μονογενοῦς υἱοῦ τοῦ θεοῦ
18
He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.

1 John 5:10

ὁ πιστεύων εἰς τὸν υἱὸν τοῦ Θεοῦ ἔχει τὴν μαρτυρίαν ἐν ἑαυτῷ ὁ μὴ πιστεύων τῷ θεῷ ψεύστην πεποίηκεν αὐτόν ὅτι οὐ πεπίστευκεν εἰς τὴν μαρτυρίαν ἣν μεμαρτύρηκεν ὁ Θεὸς περὶ τοῦ υἱοῦ αὐτοῦ
10
He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son.

2 Thessalonians 2:12

ἵνα κριθῶσιν πάντες οἱ μὴ πιστεύσαντες τῇ ἀληθείᾳ ἀλλ' εὐδοκήσαντες ἐν τῇ ἀδικίᾳ
12
That they all might be damned who believed not the truth, but had pleasure in unrighteousness.
Hebrews 3:18
Read Hebrews 3