Musnad Ahmed: Hadith 4286

The Prophet (ﷺ) said: "The millstone of Islam will stop at the beginning of thirty-five (years) or thirty-six or thirty-seven, then if they perish (after deviating) they will meet the same fate as those who perished (before them), but if they persist (in following the right path) then they will be in a good state for seventy years.”