The word(s) "slack" appears 2 time(s) in 2 verse(s) in Quran in Muhammad Habib Shakir translation.

(1) Say: If your fathers and your sons and your brethren and your mates and your kinsfolk and property which you have acquired, and the slackness of trade which you fear and dwellings which you like, are dearer to you than Allah and His Apostle and striving in His way, then wait till Allah brings about His command: and Allah does not guide the transgressing people.

(2) And be not slack so as to cry for peace and you have the upper hand, and Allah is with you, and He will not bring your deeds to naught.