Difference between ῥῆμα Θεοῦ, vs., λόγον Θεοῦ

Question

What is the difference in meaning between the NT's use of these two phrases, both translated "Word of God" (if any)?

1. λόγον Θεοῦ (only the singular not plural), Matt 15:6, Mark 7:13, Luke 5;1, 8:11, 21, 11:28, John 10:35, Acts 4:31, 6:2, 7, 8:14, 11:1, 12:24, 13:5, 7, 46, ... Heb 4:12, 5:12, 13:7, 1 Peter 1:23, etc
2. ῥῆμα Θεοῦ (only the singular not plural), Luke 3:2, John 3:34, 8:47, Eph 6:17, Heb 6:5.

What consequences (if any) does this have for the understanding of Eph 6:17?

Take the helmet of salvation and the sword of the Spirit, which is the word of God.

Answer 1

A quick rule of thumb is the following:

• In all the verses where λόγος ϑεοῦ appears, try to replace "word"
  with "message", or "order" or "command", depending on the context

• In all the verses where ῥῆμα ϑεοῦ appears, try to replace "word" with "utterance", or "call"

In Heb 5:12 we do not find λόγος, but λόγιον, which is best translated "oracle".

In John 3:34 the expression τὰ ῥήματα τοῦ θεοῦ (literally "the words of God") spoken by the Christ, are implicitly contrasted with the words of God spoken by the prophets, because, while God gives the Spirit to the prophets "by measure", he gives the Spirit to the Christ "without measure".

In John 8:47 Jesus Christ reproaches the Jews who contend with him because they do not listen at all to τὰ ῥήματα τοῦ θεοῦ ("the words of God"), best translated - as the NIV does - with "what God says".

In Heb 6:5, θεοῦ ῥῆμα, "God's word", is what Christ has said on behalf of God. Once tasted, there is no hope to be "renewed in repentance" for those who "fall away".

In Eph 6:17, ῥῆμα θεοῦ, the "word of God" is the "sword of the Spirit", that is the word that God inspires is the weapon to be used in spiritual combat.

Answer 2

λόγον Θεοῦ (logos,) and ῥῆμα Θεοῦ (rhema)

The difference is well worth understanding, although it depends on your theology. Man is a spirit, posses a soul, and lives in a body. And, man can ‘hear/see’ with his physical ‘ears/eyes’, but, can also ‘hear/see’ with his spiritual ‘eyes/ears’. Your ‘soul’, that part of you that ‘acts/does’, that part that ‘moves’ or ‘motivates’ the body [will] can listen to, and act on either - that is, can be motivated by your spirit, or your body.

Jesus often exclaimed ‘you have ears, but cant hear, eyes, but can’t see’. This referenced what I briefly tried to explain. And, Paul exhorted believers to ‘live in the spirit’.

Now back to the question. Logos you hear with your ‘physical’ ears. So you naturally hear it, and the either reject/accept/contemplate/meditate and then possibly act on it.

We see that in Luke 5:1 (λόγον Θεοῦ)

LUKE 5:1 So it was, as the multitude pressed about Him to hear the word of God

If we look a little further down, in verse 5, we see ῥῆμα Θεοῦ

LUKE 5:5 But Simon answered and said to Him, “Master, we have toiled all night and caught nothing; nevertheless at Your word I will let down the net.”

Here we see Peter firstly reasoning out what he heard Jesus say, but then his spirit ‘perceived [saw]’ ‘something’, and then he acted on the word. Rhema is when your ‘inner man’ [spirit] causes you to ‘act’

Essentially, the word of God [Logos], in and of itself will have no ‘effect’, [or ‘life’] until your spirit ‘sees’ it. This is what revelation is/means. Revelation is when your spirit ‘sees’ or ‘hears’ the word. So , Rhema refers to spiritual hearing/seeing. And it is when that occurs that the ‘word’ has ‘life’.

Now this difference becomes clear in the Ephesians passage you list

EPH 6:17 And take the helmet of salvation, and the sword of the Spirit, which is the word of God;

And, consider the following ...

HEB 4:12 For the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit,

It is important for believers to ‘listen’ to their spirit. That ‘word’ which their ‘spirit’ has ‘seen’ - what some refer to as ‘believe in your heart’ - which often conflicts with what your ‘natural’ eyes are seeing. The Ephesians passage is exhorting believers to rest in what their spirit [rhema] knows, that ‘word that is in your heart’, what you ‘believe’. What you ‘know’ [perceive in your heart/spirit]. When you hear/read Logos, there are times your [natural] reasoning will conflict with what your heart [rhema] is saying, as with Peter in that Luke incident, but rhema leads to life.