Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear.
Ephesians 4:29 (ESV)
Let no corrupting talk come out of your mouths … Worthless and impure words should not come out of your mouths, because they are incompatible with your new life in Christ. However, this will only happen, when these kinds of words and the correspondent thinking are not in your hearts. What is in, will come out! Jesus explained it like this: For out of the abundance of the heart the mouth speaks. The good person out of his good treasure brings forth good, and the evil person out of his evil treasure brings forth evil (Matthew 12:34f).
As a first step the Holy Spirit renewed your hearts in the new birth. He gave you a desire for sanctification and the mind of Christ (1 Cor 2:16). Your responsibility now is to like what Christ likes and to hate what He hates. Fill your hearts with whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable … (Phil 4:8). It’s helpful to carefully consider every word in this list in order to know what pleases Christ and with what to fill your souls. When you cooperate with the Spirit, when you fill your hearts and minds with the Word of God and confess every worthless word that slips out, over time the result will be a true Christian way of speaking.
… but only such as is good for building up … The goal of your speech should be instructive and uplifting. This is especially important in ministry, with regard to co-workers and volunteers. The tongue of a disciple will build others up, while worthless and hurting words will poison your relationships and destroy your ministry.
… as fits the occasion … The children and teenagers you meet in your ministry are often on different levels of understanding. Some know very little and you need to teach them the basics in simple words. When they grow older or mature, they will need more solid food and can be taught whole concepts of good theology, which will help them defend their faith before their peers or at school. The tongue of a disciple speaks as fits the occasion, according to the needs of a particular group.
… that it may give grace to those who hear. In the context of this verse grace is edifying grace. It comes from God through the mouth of a disciple to bring those who hear closer to the Lord, to increase their knowledge, strengthen their faith, deepen their affection for Christ and motivate them for Christian living and ministry. How beneficial to children and adults is the tongue of a disciple that is influenced, controlled and used by God!