Is it permissible to do a spell for a good purpose, like making someone love his wife, by resorting to a magician?

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.

If the questioner means going to a diviner or magician who claims to have insight into matters of the Unseen and who writes Satanic amulets, perform incantations, and the like, this act is impermissible and the perpetrator exposes himself to a great risk by doing so. It is even forbidden to ask them about anything. In this regard, it was reported on the authority of some of the wives of the Prophet, sallallaahu ‘alayhi wa sallam, that he warned  Muslims who consult soothsayers that their prayers would not be accepted for 40 nights. [Muslim]

Moreover, it is worse to believe in a diviner's words. Referring to this, it was reported on the authority of Abu Hurayrah that the Prophet, sallallahu ‘alayhi wa sallam, warned Muslims who consult soothsayers and believe what they say, that by doing so they have disbelieved in what was revealed to Muhammad, sallallaahu ‘alayhi wa sallam. [Abu Daawood, Ibn Maajah and Ahmad]

Unfortunately, this is a common practice intended to increase love between spouses.

However, if the questioner means pursuing this purpose by asking for the supplications of those who are known for their goodness, righteousness and uprightness, then it is permissible. This is because this is included in the permissible types of Tawassul (supplication through an intermediary).

Allaah Knows best.