If someone who used to pray the five daily prayers, stopped and after a long time, he began praying, what can happen to him on this life and the day of judgement?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

This person must fear Allah Almighty and know that it is Allah Who has made performing the prayer an obligation, and know that our lives are in His Hands. So, one has to glorify Him and be aware of His Anger and indignation. Then, this person has to know that the prayer is the second pillar upon which Islam is built and negligence in performing it leads to negligence of all other precepts and teachings of Islam. This person also should know that the Muslim scholars differed in opinion about whether the one who neglects performing the prayer is a Muslim or not. Is he pleased to be concerned by such a stand from the scholars? I think no Muslim accepts that.

Thereupon, such a person has to make up all the missing prayers if he recognizes their number and can do that without hardship, and then, seek Allah's support to help him stick to Islam and to take good friends, who may help him in doing righteous actions. As for what will happen to him in this world, he may breath his last while in a state of negligence of performing the prayer, which brings out Allah's anger. Also, in the next life, only Allah knows his situation.

Allah Says (what means):

•   {Maintain with care the [obligatory] prayers and [in particular] the middle prayer and stand before Allah, devoutly obedient.} [Quran 2:238]

•   {And when you have completed the prayer, remember Allah standing, sitting, or [lying] on your sides. But when you become secure, re-establish [regular] prayer. Indeed, prayer has been decreed upon the believers a decree of specified times.} [Quran 4:103]

 Finally, this person has to know that only commitment to Allah's Orders and His Prophet's Sunnah that can bring him out to happiness and bliss.

Allah knows best.