Greek word · G2925

κρούω

krouō

to knock

To strike, and especially to knock at a door to be let in.

Appears 9 times in 9 verses of the Greek New Testament. · Updated November 01, 2026

What it means

Κρούω

[in LXX: before ἐπί Judges 19:22, Song of Songs 5:2 (דָּפַק) ;]

with, accusative, τ. αὐλαίαν, Judith 14:14 * ;]

to strike, knock: at a door (Κόπτειν, in Att..), Matthew 7:7-8, Luke 11:9-10 12:36, Acts 12:16, Revelation 3:20; with accusative, τ. θύραν, Luke 13:25, Acts 12:13.†

(AS)

From G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922), via STEPBible.org (CC BY 4.0).

Range of meaning: To strike, and especially to knock at a door to be let in.
Against the English: "Knock" is exact. English readers may hear only a polite tap, but the Greek word itself says nothing about how loud or how long the knocking is.
Used elsewhere in the period: Ordinary door-knocking in Judges 19:22 and Song of Songs 5:2 in the Greek Old Testament, and in Acts 12:13, where Peter knocks at a gate. Luke pairs knocking and opening at 12:36 (servants open at once for their master) and at 13:25, where the door has been shut and those knocking are refused. Later rabbinic writings use knocking at the gates of mercy as a picture of prayer, but these are later than Jesus and can only illustrate the idea.

Range of meaning: To strike or knock, especially at a door to be let in. In the New Testament it is always used of knocking at a door.
Against the English: BSB, NIV and NLT add "the door" in the promise ("the door will be opened"); KJV, ESV and YLT keep the Greek's "it will be opened." Adding the word is fair, since the door is implied, but in English "knock and doors open" is now a proverb about opportunity, which is not the picture here.
How it drifted: In popular English, "knock and the door will be opened" has become a motto for careers and opportunities. The original picture is a person at a householder's door at night asking for help (vv. 5–7), standing for a disciple coming to God.
Used elsewhere in the period: Luke 12:36 (servants open as soon as their master knocks); Luke 13:25 (people knock at a door already shut, "Lord, open to us"); Acts 12:13 (Peter knocking at the gate); Rev 3:20 ("I stand at the door and knock"); LXX Song 5:2 (the beloved knocks at the door). Later rabbinic texts also use knocking at a door as an image for prayer, though these date after the New Testament.

Range of meaning: Krouō: to knock, strike (as on a door). Anoigō: to open. Together they form a common pair: knocking, then the door being opened.
Against the English: English "knock … open" is accurate. What a modern reader may miss is the setting: at night a house was shut and barred from inside, and someone had to be awake to let anyone in.
Used elsewhere in the period: The same pair appears in Luke 11:9–10 ("knock, and it will be opened to you"), 13:25 (the householder who has shut the door and will not open), and Acts 12:13–16 (Peter knocking and the servant girl Rhoda answering). Rev 3:20 ("I stand at the door and knock") uses the same image. Compare also the doorkeeper commanded to stay awake in Mark 13:34.

Matthew · 2

Matthew 7:7 κρούετε, do knock

Ask, and it will be given to you; seek, and you will find; knock, and the door will be opened to you.

Here: "Knock." The everyday act of someone standing outside a closed house door and asking to be let in. It is a picture of prayer as approaching a household and asking to be admitted.
Matthew 7:8 κρούοντι knocking

For everyone who asks receives; he who seeks finds; and to him who knocks, the door will be opened.

Here: Knocking on a door, the action of someone outside a house asking to be let in or helped. The present form again pictures someone who is knocking.

Luke · 4

Luke 11:9 κρούετε, do knock

So I tell you: Ask, and it will be given to you; seek, and you will find; knock, and the door will be opened to you.

Here: To knock or rap on a door to ask for entry. It continues the picture from vv. 5–7, where a man stands at a neighbour's bolted door at midnight. Present command: knocking as something you do and keep doing.
Luke 11:10 κρούοντι knocking

For everyone who asks receives; he who seeks finds; and to him who knocks, the door will be opened.

Here: Knocking at a closed door, the ordinary way of asking to be let in. The image follows directly from the shut door of the friend at midnight in verses 5-8.
Luke 12:36 κρούσαντος having knocked

Then you will be like servants waiting for their master to return from the wedding banquet, so that when he comes and knocks, they can open the door for him at once.

Here: "And has knocked." The house is shut and barred for the night, and the master knocks at his own door expecting someone inside to be awake and ready.
Luke 13:25 κρούειν to knock

After the master of the house gets up and shuts the door, you will stand outside knocking and saying, ‘Lord, open the door for us.’ But he will reply, ‘I do not know where you are from.’

Here: A present infinitive, so the knocking goes on and on. The same verb appears in Luke 11:9–10 ('knock and it will be opened'), which makes the reversal here hit hard.

Acts · 2

Acts 12:13 κρούσαντος When was knocking

He knocked at the outer gate, and a servant girl named Rhoda came to answer it.
Acts 12:16 κρούων· knocking;

But Peter kept on knocking, and when they opened the door and saw him, they were astounded.

Revelation · 1

Revelation 3:20 κρούω. knock.

Behold, I stand at the door and knock. If anyone hears My voice and opens the door, I will come in and dine with him, and he with Me.

Here: Present tense: "I keep knocking." It is the ordinary sound of a guest or a returning master asking to be let in (compare Luke 12:36; Song of Songs 5:2 in the Greek).

Word data: STEPBible.org (CC BY 4.0), main text only.