Be ye therefore very courageous to keep and to do all that is written in the book of the law of Moses, that ye turn not aside therefrom to the right hand or to the left;

Only take courage, and be careful to observe all things that are written in the book of the law of Moses: and turn not aside from them neither to the right hand nor to the left:

and ye have been very strong to keep and to do the whole that is written in the Book of the Law of Moses, so as not to turn aside from it right or left,

So be very strong to keep and do whatever is recorded in the book of the law of Moses, not turning away from it to the right or to the left;

Even so, be strengthened and be careful that you observe all the things that have been written in the book of the law of Moses, and that you do not turn aside from them, neither to the right, nor to the left.

Robrate igitur vos valde, ut custodiatis, et faciatis quicquid scriptum est in libro Legis Mosis, ut non recedatis ab eo neque ad dextram, neque ad sinistram.

Be you therefore very courageous, etc He now shows them the mode of conquering, -- not to indulge gross security, as too often happens, as a substitute for genuine confidence. He affirms that God will be propitious to them, and promises that whatever they attempt will turn out prosperously, provided they are steadfast in obeying the Law. However confidently hypocrites may contemn and deride God, they would wish, however, to have him astricted to them; nay, they often, with no small pomposity, boast of his promises. But true faith, while it reclines upon God, keeps those who possess it in his fear. In short, those who would find God must seek him sincerely, and if we desire to be regarded by him, we must beware of turning our backs upon him. The expression, Be you very courageous, as has elsewhere been said, denotes serious study, because in the great weakness of our nature no man will set about the thorough observance of the Law, if he does not exert himself above his strength. Attention ought also to be paid to the definition of true obedience which is here repeated from Moses, (Deuteronomy 5:32) and said to consist in not turning either to the right hand or the left.

Be ye therefore very courageous to keep and to do, etc. - It requires no small courage to keep a sound creed in the midst of scoffers, and not less to maintain a godly practice among the profane and profligate.
That is written in the book - By the word of God alone his followers are bound. Nothing is to be received as an article of faith which God has not spoken.

Be ye therefore very courageous to keep and to do all that is written in the book of the law of Moses,.... To observe which required spiritual strength, fortitude of mind, a holy courage, a firm and fixed resolution, and particularly to destroy the Canaanites required in that book, and to abstain from all communion and fellowship with them:
that ye turn not aside therefrom, to the right hand or the left; See Gill on Joshua 1:7.

Very courageous - For it will require great courage and resolution to execute all the commands of Moses, and particularly, that of expelling and destroying the residue of the Canaanites. The right hand or the left - That is, in one kind or other, by adding to the law, or diminishing from it.