Is it permissible to lie in order to guide someone to the right path? For instance, can I claim to have seen this person being punished in a dream?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

First of all, we would like to thank the questioner for his keenness on guiding others. However, we would also like him to know that lying is an quality, and the Prophet, sallallaahu ‘alayhi wa sallam, warned us against it, and informed us that lying leads to wrongdoing, which in turn leads to Hell, and that when a man keeps on lying, he is recorded with Allaah as a liar. [Ahmad, Muslim and At-Tirmithi]

Therefore, it is not permissible to lie because Da‘wah can be conveyed in many other ways. You may try to guide this person through the lawful methods stated by Allaah in the verse (which means): {Invite to the way of your Lord with wisdom and good instruction, and argue with them in a way that is best.} [Quran 16:125]

If these methods fail, then a false dream would certainly be of no effect on him either. We ask Allaah to guide us all to what He likes and to what pleases Him.

Allaah Knows best.