-Can the Promise of G-d Keep the People Holy?

"Can the Promise of G-d Keep the People Holy?"

Before delivering the admonition, Moses conveys the blessings of G-d to the Jewish people, including the blessing that G-d will establish His people to be a holy nation to Him. The Haamek Davar sees these words as G-d's promise to protect those who are faithful to Him, even though they may be involved in mundane communal affairs. Is this blessing a foolproof guarantee?