The Jews and Christians do not dye (their grey hair), so do the opposite of what they do

Explanation

Abu Hurayrah (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) told the Companions that the Jews and Christians do not dye their hair or beards; rather, they leave grey hair as it is. So he ordered them to do the opposite of what the Jews and Christians do by dying their hair and beards.