"Work for your terrestrial life in proportion to your location in it, and work for your afterlife in proportion to your eternity in it." This is part of the advice that the great theologian and mystic Abu Hamid al-Ghazali put down in his Letter to a Disciple (Ayyuha l-Walad). Considered to be the spiritual last will and testament of al-Ghazali, Letter to a Disciple is a summary of the spiritual teachings of he who was regarded as the Proof of Islam . Written towards the end of his life, Letter to a Disciple was composed in response to the request by a disciple for the master to write down in a few pages a summary of all his teachings. The main ideas running throughout the work are on acquiring knowledge which is of spiritual benefit, purifying the intention, and acting on the basis of the acquired knowledge. Referring extensively to the example of the Prophet and to that of the early Sufis, al-Ghazali gives us a work of great depth, beauty and simplicity. This new translation is presented here as a bilingual English-Arabic edition. The Arabic text is fully vocalised and the whole book is therefore suitable as a reader for students of Arabic.