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.
We did not find any sound evidence from the Quran or the Sunnah stating that 700 prayers of the person who steals are not accepted. As for saying that the person will not be asked about his prayers on the Day of Judgement, this is not true.
Abu Hurayrah narrated that the Prophet said: “The person will be first judged about his prayer, if it is valid, he is the successful, the prosperous; if it is invalid, he is the loser, the disappointed…” [Abu Daawood, and At-Tirmithi]
Bringing the person to account on the Day of Judgement about his prayer does not mean that he will not be judged about other deeds. In fact, his good deeds will be weighed along with his bad deeds. So, if his good deeds outweigh his bad ones, he enters Paradise, otherwise he enters Hellfire unless Allah forgives him. Now, he can then be taken to Paradise after receiving the punishment he deserves for these bad deeds provided he has the tenets of belief. The evidence for this is the Hadeeth reported by Al-Bukhaari and Muslim which reads: “When the people of Paradise will enter Paradise and the people of Hellfire will go to Hell, Allah will order those who have had faith equal to the weight of a grain of mustard seed to be taken out from Hellfire. So, they will be taken out but (by then) they will be blackened (charred). Then they will be put in the river of Hayat (life), and they will revive like a grain that grows near the bank of a flood channel.”
As for those who claim that the person who enters Hellfire stays there forever (who are the Khawaarij), they are wrong because they deny intercession and claim that the sinful people dwell in Hellfire forever, but this is contrary to the belief of Ahlus-Sunnah wal Jamaa'ah.
As for the person who enters Paradise, he stays in it permanently as Allah Says (what means): {No fatigue will touch them therein, nor from it will they [ever] be removed.} [Quran 15:48]
May Allah grant us Paradise.
Allah knows best.