‘You will keep them, O YHWH.
You will preserve them from this generation for ever.
The wicked walk on every side,
When vileness is exalted among the sons of men.'
So through His word YHWH will keep His people and will continue to preserve them through the generations for ever. His words are the perfect antidote to unbelief, sin and deceit.
But meanwhile sin will continue to walk abroad, the unrighteous will appear to be on every side, and vileness will be exalted among men. They will boast about it. God is not deceived about the human race. He knows what men are. Thus must the godly look constantly to the word of God, and God will then preserve and keep them. Note that the opening ‘You' is emphatic, for in the end it is only YHWH Who can keep His own and enable them to persevere.