'Slack' in the Bible
And repays those who hate Him to their face, by destroying them; He will not be slack to him who hates Him, but will requite him to his face.
When you make a vow to the Lord your God, you shall not be slack in paying it, for the Lord your God will surely require it of you, and slackness would be sin in you.
Joshua asked the Israelites, How long will you be slack to go in and possess the land which the Lord, the God of your fathers, has given you?
Be strong, therefore, and let not your hands be weak and slack, for your work shall be rewarded.
He becomes poor who works with a slack and idle hand, but the hand of the diligent makes rich.
He who is loose and slack in his work is brother to him who is a destroyer and he who does not use his endeavors to heal himself is brother to him who commits suicide.
Now we charge you, brethren, in the name and on the authority of our Lord Jesus Christ (the Messiah) that you withdraw and keep away from every brother (fellow believer) who is slack in the performance of duty and is disorderly, living as a shirker and not walking in accord with the traditions and instructions that you have received from us.