Passage
He that shall gainsay thy mouth, and not obey all thy words, that thou shalt command him, let him die: only take thou courage, and do manfully.
He that shall gainsay thy mouth, and not obey all thy words, that thou shalt command him, let him die: only take thou courage, and do manfully.
Joshua 1:16 And they made answer to Joshua, and said: All that thou hast commanded us, we will do: and whither soever thou shalt send us, we will go.
Joshua 1:17 As we obeyed Moses in all things, so will we obey thee also: only be the Lord thy God with thee, as he was with Moses.
Joshua 1:18 He that shall gainsay thy mouth, and not obey all thy words, that thou shalt command him, let him die: only take thou courage, and do manfully.
The verse centers on "shall", "gainsay", "mouth", "obey", "words", "thou", "shalt", and "command". It is saying that the verse draws attention to "shall" and "gainsay", so its meaning should be read from those terms before moving to application.
The prior verse says "As we obeyed Moses in all things...", giving immediate footing for "shall" and "gainsay". In Joshua context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "shall" and "gainsay" with trust shaped by these words, not by a vague optimism outside the passage.