in fatawa afriqah, alahazrat says:
Q: what is the ruling concerning the imam of masjid (pesh-imam) who makes amulets (ta'widh)?
A: There is no harm in amulets (ta'widh) that are permissible - such as those in which Quranic verses are written, or the Glorious Names of Allah, or other prayers and litanies [adhkar, da'waat].
In fact, it is desirable to do so, because RasulAllah sallAllahu alayi wa sallam has said in a similar situation: "Whoever can benefit his brother, then he should give him that benefit". Imam Ahmad and Muslim report from Jabir raDiyAllahu anhu.
As for names of Prophets and Awliya'a - may the blessings of Allah be upon them: it is permissible to make an amulet with their names with the intention of blessings [tabarruk] and intercession [tawassul] - as their names are manifestations of the blessings from the Glorious Names of Allah.
In Durr Mukhtar it is written:
"The ruling in Mujtaba is that amulets that are written in a language other than Arabic are disliked [makruhah]"
In Radd al-Muhtar (commenting on the above):
There is no harm [laa ba'as] in amulets if the Quran is written in them, or the Divine Names of Allah. What is disliked when it is not in the Arabic tongue is when its meaning is not known. And mayhap, magic or disbelief (siHr or kufr) is present in those words. As for those (amulets) in which the Quranic verses are written or prayers, there is no harm in it at all.
and he also cites Mujtaba thus:
In our age, it is deemed an practice and the ruling is that of permissibility; and reports [aathaar] have been mentioned in this regard".
Imam Nawawi in his Sharh Muslim says:
Those amulets (ruqaa) in which the speech of disbelievers is written, and the amulets which are undecipherable (either in an unknown language or the words are not known) are deplorable because of the possibility (iHtimal) that it might be disbelief (kufr) or close to it; such amulets are disliked (makruh).
As for the amulets which contain verses of the Quran or well-known adhkar (prayers), there is no prohibition in it anyhow.
in the same work, it is mentioned:
There is an ijmaa (scholarly consensus) on the permissible of amulets containing verses of the Quran and adhkar invoking the Divine names of Allah.
In Ashi'atul Lam'aat, the commentary on Mishkat:
Ruqiyah (amulets) using the verses of the Qur'an and the Divine Names of Allah are permissible, according to all scholars (ba-ittifaq). Apart from these, if the amulets contain words whose meaning is not known or if the meanings contradict the religion and shariat, then they are NOT permissible.
[Alahazrat says:]
Of course, those amulets which are known to be irreligious and bad - for example, some amulets have the names of: shaytan, fir'awn, haaman, nimrod - or there are words whose meaning is unknown (maj'hul) such as the amulet written to ward off epidemics in which it is written:
bismillah - susa, haasusa, masusa
and some other amulets to ward of hardships in whcih it is written:
aliqa maliqa taliqa anta ta'alam ma fi'l qulubi haqiqa
THESE ARE IMPERMISSIBLE.
however, if there are some words whose meaning is not known, but are attributed to prominent awliya or reliable scholars - who are experts in both external and esoteric knowledge, and when such an attribution is authentic (handed down by reliable narrators) - in such case, those words will be accepted only by relying upon the aforementioned esteemed personalities (else they will not be accepted).