Like Matthew 24 and Mark 13, Luke 21 is addressed to Christ’s disciples: those who have asked the question that prompted this message. Throughout the chapter he speaks to them as he would only speak to those who follow him, encouraging their faith and their testimony, teaching them how to respond to persecutors, warning of hatred from the world for his name’s sake, showing them how to regard this world, and directing them how to escape from Jerusalem when its judgment comes.
Is it necessary for true believers to receive these warnings? Evidently it is, or else the warning would not need to be given. The approach of sin is gradual, and gradually the believer may adjust his standards, and allow what he did not allow before. We are to watch lest our hearts be overcharged with these things, and the word means weighed down or burdened. Sin and temptation are always there, but the effect of them has built up over time, until the impulse is so strong that it is no longer resisted. There was a lack of persistent resolve in rejecting the suggestions of the flesh. The danger does not diminish over time. Satan fights a long campaign against us, and we need to grow stronger not weaker in repulsing his approaches. There is great danger in counting ourselves beyond the reach of temptation. Nevertheless, God will keep his own.
The remedy is that we take heed to ourselves. Vigilance is required – ‘lest at any time’ – and the words imply that it is never safe to relax, to take a holiday from resisting the devil and sin within us. We must guard our hearts, and guard every thought. When we fall, we must repent quickly. Sin can never watchfulness, as if some time off watchfulness would allow us to build up our strength again for the battle.
Throughout the verse the reality is in view that Christ is coming again. That is the day that should always be in our minds. It is when we forget that day that our lives start to go to pieces, because that day gives us a perspective on life that teaches us what is important. ‘And so that day could upon you unawares.’ You know in theory that it is coming, but you are no longer looking out for it. Of course, we do not know the day when Christ will return, nor even the year. How then can we avoid the day coming upon us unaware? Surely, it is bound to do so. No, it is not, for the preparation we need is not to have that day marked in our diaries, but to be living for God every day of our lives. Then we will be ready whenever that day comes. We will be looking forward to it, and living in a way that pleases our Lord whenever he comes.