Jude had a message to pass on to his friends, possibly converts from one of his mission journeys.  We do not know who they were but Jude felt a deep spiritual responsibility for them to stay true to the gospel.  The gospel is not a flexible or dynamic concept, bending to each wave of social opinion.  It was given by the Lord Jesus and defined by the apostles as one clear doctrine to be handed down unchanged to each generation.  However, already, false teachers had infiltrated the churches with a different gospel (Galatians 1:6-9).  

That brought two urgent matters to the top of Jude’s concern.  One was to encourage believers to stand firm in the salvation they received after believing the gospel (1 Peter 5:12).  The other was that they should not be silent about the truth, allowing false teaching to take root unopposed.  These young churches and their leaders needed to proclaim the gospel, persuading people of its truth, and publicly exposing false teachers (1 Timothy 1:3-7).

Godless living is attractive to worldly people and can easily seduce the spiritually immature into compromise.  In any culture, once a few leading people say that something is right, many will follow them (Jude 1:17-19).  It is a broad road which leads to destruction (Matthew 7:13), and it takes courage to stand out from the crowd and say that their ‘new truths’ are ‘old lies’.  People can secretly slip into a church presenting themselves as believers or even teachers (2 Peter 2:1).  Initially they will say the right things, but will make friendships of vulnerable and discontented people to establish a foothold (Matthew 7:15).  Others may think they are kind and loving, but their poison will soon start flowing (2 Timothy 3:1-8).  Even when they draw people away from the truth, many believers will feel it is unkind to challenge or rebuke them.  Not so.  Unless they are stopped, the gospel is at risk.

Such problems have not gone away.  Today’s churches are constantly at risk of being pulled away from the true gospel. False teachers are more common than many think (2 Timothy 4:3-4).  They may sound wise and behave with a kindly authority at first and so are rarely challenged (Titus 1:10-13).  But discerning believers will see that they are drawing people to themselves and not to Jesus: they encourage fleshly behaviour, often saying that God wants people to be happy or healthy, wealthy or powerful.  The first line of defence against their influence is to be confident of salvation by grace alone, and to live in a way that will please the Lord, as defined in the Scriptures.  The second vital protection for the church is to tell the people, from the Scriptures, why the false teachers are wrong.  The need to contend for the truth is just as urgent today, in colleges and communities, workplaces and worship places (1 Peter 5:8-9).  It is a high-risk strategy – someone somewhere will not like it; but we cannot afford to remain mute when the precious blood of Christ is being despised and false gospels are deluding thousands (Hebrews 10:29).