Without fail
Definition 1 of 1
Pro Tip 1/3Commitment Emphasis
Used to stress the commitment to do something and the importance of not failing to do it. 
I will deliver your package tomorrow without fail.
Pro Tip 2/3Expectation Setting
Communicates a strong expectation and the speaker's confidence that something will happen. 
The train leaves at 8 a.m. without fail.
Pro Tip 3/3Urgency Conveyed
Used to express the urgency and non-negotiable nature of a deadline or requirement. 
Submit your application by Friday without fail.