IS IT NOT time that the hearts of all who have attained to faith should feel humble at the remembrance of God and of all the truth that has been bestowed [on them] from on high,22
lest they become like those who were granted revelation aforetime,23
and whose hearts have hardened with the passing of time so that many of them are [now] depraved?24
I.e., "Should not the remembrance of God and His revelation make them humble rather than proud?" This is an emphatic warning against all smugness, self-righteousness and false pride at having "attained to faith" - a failing which only too often attains to such as consider themselves "pious".
This is apparently an allusion to the spiritually arrogant among the Jews, who regard themselves as "God's chosen people" and, therefore, as predestined for His acceptance.
I.e., so that now they act contrary to the ethical precepts of their religion: implying that the purpose of all true faith is to make man humble and God-conscious rather than self-satisfied, and that a loss of that spiritual humility invariably results in moral degeneration.