God specified the timing for daily five times prayers and advised people through the prophet to maintain the timing strictly and ask their family members to do the same!

Verses 129-132 of Chapter 20

Had not a decree been fore-ordained by your Lord and a term for respite been appointed, judgment on them would have been passed now immediately. Therefore O Muhammad, endure what they say and glorify your Lord with His praise before the rising of the sun and before its setting, and glorify Him during the hours of the night and at the extremes of the day: perhaps you may feel satisfied. And do not cast an envious look at the worldly property We have bestowed on different kinds of people, for We have given them all that to put them to trial, and the lawful provision of your Lord is better and more lasting: enjoin Salat on the members of your family and yourself also observe it strictly. We do not ask any provision of you, for it is We Ourselves Who give you provision. And the ultimate good is for piety.