Does sin hinder one's ability to speak God's word?

From the comments of other answers, it appears that you are asking if a Christian has sin in their life, does it inhibit us from communicating the Gospel. If this is the question, then The answer is No. See the book of Jonah. In this book we have a man who unapologetically ran from God and harbored hatred of the Ninevites before during and after his preaching and call to repentance. When they do repent, Jonah is even angry about it and God has an conversation with him about how it is not right that he should be angry about the Ninevites' repentance. Jonah never repented, yet God still used him. In the book of Numbers, God even uses a donkey to spread his message (Numbers 22). If he can use an ass to reach others, he can certainly use me.

Well I think the answer is yes! When Jesus Christ rose from the dead, he freed us from sin. If we're struggling with a sin (eg/ an addiction), it's right to know that He is able to get you out of it and that when you confess your sins contritely to Him, you are made anew. You can preach. Just giving up on sharing the word would be like accepting that you are stuck in sin for life ( different from you do not sin) and there's no going back and can even lead to you drifting farther from His word and falling into the hands of the enemy. That being said, I think we can preach the gospel if we sin, if we focus on the fact that we are no more going to live a life of sin but as we share the Word with the brethren and focus our eyes on Jesus, we are being changed into the image and likeness of God.

This seems to be a pertinent passage on the topic

1 Cor 13:1-3 (RSVCE) The Gift of Love 13 If I speak in the tongues of men and of angels, but have not love, I am a noisy gong or a clanging cymbal. ² And if I have prophetic powers, and understand all mysteries and all knowledge, and if I have all faith, so as to remove mountains, but have not love, I am nothing. ³ If I give away all I have, and if I deliver my body to be burned, but have not love, I gain nothing.

And from the LORD himself

John 15:5 (RSVCE) ⁵ I am the vine, you are the branches. He who abides in me, and I in him, he it is that bears much fruit, for apart from me you can do nothing.

Matt 12:30 (RSVCE) ³⁰ He who is not with me is against me, and he who does not gather with me scatters.

Examples in recent memory

cf. Catholic Church sexual abuse scandal, which without doubt has brought much harm to souls, done a lot of damage to the Church, to her standing, and her ability to spread her spouse and LORD's message.

And in the news recently: Bishop Kieran Conry says he is ‘relieved’ after resignation | CatholicHerald.co.uk. His own words:

“In some respects I feel very calm. It is liberating. It is a relief. I have been very careful not to make sexual morality a priority [in his sermons]."

We know that the ministries of some notorious names from this list - (Obtain them from webs returned from Google search: List of scandals involving evangelical Christians) - collapsed after they were disgraced.

Anecdote

At one parish I belonged to and attended Mass, a visiting priest, high up in the diocese, said Mass and preached the homily. He was articulate and very funny, and doctrinally solid. For some reason, his homily 'was noisy to my ears', and never registered. Not long after that, he left the priesthood.

Your question is a little more complicated than one might think at first blush!

"Bad people" are the operative words, in my opinion. Bad people may attempt to preach and teach God's Word, but they do so for base motives, which could include (but are not limited to) the following:

• money

• fame

• power

• lust for any of the above, and/or lust for sexual immorality, such as the "man of God" who takes advantage of his female followers

The Bible calls bad men (and bad women) who attempt to preach and teach God's Word with their own particular and sinful slant "false teachers." The task of mature Christian believers, such as elders, deacons, pastors, ministers, priests, and so on, is to be on guard for false teachers and to protect the flock from these predators, whom Jesus called "ravenous wolves" in Matthew 7:15; 10:16; and Luke 10:3.

The important word in the last sentence is, I suggest, mature. Spiritual maturity in a church leader means in part that he or she is able to confront and refute false teachers with sound doctrine and teaching.

"[Elders] must pay attention to the reliable message as it has been taught to them so that they can encourage people with healthy instruction and refute those who speak against it" (Titus 1:9 CEB).

Is it possible for an ungodly man or woman to benefit spiritually a hearer or two now and then? Yes, I believe so. The writer to the Hebrews tells us that God's word is

"living and active and sharper than any two-edged sword . . . [and] able to judge the thoughts and intentions of the heart" (Hebrews 4:12, excerpts, NASB Updated).

False teachers may even lead with truth (in the sense of starting with the truth), and then follow up with a partial truth or a distortion of the truth. The truth with which they "lead" might be straight Scripture. The simple quoting of a Scripture could make all the positive difference in the life of a person, particularly if he or she extracts themselves from the false teacher soon enough!

Interestingly, the apostle Paul had an interesting perspective on preachers and teachers who preach and teach with the wrong motives. Paul said,

"Some indeed preach Christ even of envy and strife; and some also of good will: the one [do it] of love, knowing that I am set for the defence of the gospel; but the other proclaim Christ of faction, not sincerely, thinking to raise up affliction for me in my bonds. What then? only that in every way, whether in pretence or in truth, Christ is proclaimed; and therein I rejoice, yea, and will rejoice" (Philippians 1:15-18 ASV).

Is there a difference between "bad people" (i.e., false teachers) and preachers who are perhaps correct doctrinally but are in need of an attitude adjustment? Yes, I think so. Nevertheless, we need to adopt Paul's perspective in this matter and rejoice because Christ is being preached. Competition, even among preachers, can be a good thing!

Addendum:

Quite simply (but not to derogate your question), communicating the Word of God requires a clean vessel. Yes, even a person who is harboring and hiding a besetting sin can still preach and teach, but the hypocrisy of attempting to preach the truth while living a lie will eventually catch up with him or her, and the result could be his or her exposure, and with exposure comes (for example) losing one's ministry. Even with repentance, the person may not be able to return to a fruitful ministry, partly because of personal factors, and/or partly from people's lack of trust in the messenger.

Marshall McLuhan was definitely onto something when he said, "The medium IS the message." You cannot separate one from the other. In Christian terms, a sinful messenger is lacking in spiritual power, spiritual insight, and spiritual sensitivity. Perhaps most serious of all is the sinner's failure to glorify God as much as he could have had he not lingered in unconfessed sin.

While we all sin, and we "all stumble in many ways" (James 3:2), to glorify God we need to keep short accounts with God by confessing our sin, particularly before attempting to spread the word. Jesus condemned hypocrisy. A hypocritical spreader of the Word can do more harm than good, both to himself and to others, especially when his sin is "found out" (see Numbers 32:23).