The following is from Alexander MacLaren’s commentary on the book of Joshua.
For the Christian soldier, then, God’s law is his marching orders. The written word, and especially the Incarnate Word, are our law of conduct. The whole science of our warfare and plan of campaign are there. We have not to take our orders from men’s lips, but we must often disregard them, that we may listen to the ‘Captain of our salvation.’ The soldier stands where his officer has posted him, and does what he was bid, no matter what may happen. Only one voice can relieve him. Though a thousand should bid him flee, and his heart should echo their advices, he is recreant if he deserts his post at the command of any but him who set him there. Obedience to others is mutiny. Nor does the Christian need another law to supplement that which Christ has given him in His pattern and teaching. Men have appended huge comments to it, and have softened some of its plain precepts which bear hard on popular sins. But the Lawgiver’s law is one thing, and the lawyers’ explanations which explain it away or darken what was clear enough, however unwelcome, are quite another. Christ has given us Himself, and therein has given a sufficient directory for conduct and conflict which fits close to all our needs, and will prove definite and practical enough if we honestly try to apply it.
The application of Christ’s law to daily life takes some courage, and is the proper field for the exercise of Christian strength. ‘Be very courageous that thou mayest observe.’ If you are not a bold Christian you will very soon get frightened out of obedience to your Master’s commandments. Courage, springing from the realisation of God’s helping strength, is indispensable to make any man, in any age, live out thoroughly and consistently the principles of the law of Jesus Christ. No man in this generation will work out a punctual obedience to what he knows to be the will of God, without finding out that all the ‘Canaanites’ are not dead yet; but that there are enough of them left to make a very thorny life for the persistent follower of Jesus Christ.
And not only is there courage needed for the application of the principles of conduct which God has given us, but you will never have them handy for swift application unless, in many a quiet hour of silent, solitary, patient meditation you have become familiar with them. The recruit that has to learn on the battle-field how to use his rifle has a good chance of being dead before he has mastered the mysteries of firing. And Christian people that have their Christian principles to dig out of the Bible when the necessity comes, will likely find that the necessity is past before they have completed the excavation. The actual battle-field is no place to learn drill. If a soldier does not know how his sword hangs, and cannot get at it in a moment, he will probably draw it too late.
I am afraid that the practice of such meditation as is meant here has come to be, like the art of making ecclesiastical stained glass, almost extinct in modern times. You have all so many newspapers and magazines to read that the Bible has a chance of being shoved out of sight, except on Sundays and in chapels. The ‘meditating’ that is enjoined in my text is no mere intellectual study of Scripture, either from an antiquarian or a literary or a theological point of view, but it is the mastering of the principles of conduct as laid down there, and the appropriating of all the power for guidance and for sustaining which that word of the Lord gives. Meditation, the familiarising ourselves with the ethics of Scripture, and with the hopes and powers that are treasured in Jesus Christ, so that our minds are made up upon a great many thorny questions as to what we ought to do, and that when crises or dangers come, as they have a knack of coming, very suddenly, and are sprung upon us unexpectedly, we shall be able, without much difficulty, or much time spent in perplexed searching, to fall back upon the principles that decide our conduct-that is essential to all successful and victorious Christian life.
And it is the secret of all blessed Christian life. For there is a lovely echo of these vigorous words of command to Joshua in a very much more peaceful form in the 1st Psalm: ‘Blessed is the man that walketh not in the counsel of the ungodly, . . . but his delight is in the law of the Lord, and in His law doth he meditate day and night’-the very words that are employed in the text to describe the duty of the soldier-therefore ‘all that he doeth shall prosper.’