In the wisdom literature of the Old Testament, we are told that as iron sharpens iron, so one man sharpens another (Proverbs 27:17).
Katika habari za hekima katika agano la kale tunaambiwa ya kwamba chuma hunoa chuma mwenziwe, vivyo hivyo mtu huchangamsha sura ya rafiki yake (Methali 27:17) “kamba ya nyuzi tatu haikatiki rahisi.”