Here are several extracts from a letter that Seyyidina Sheikh Ahmed Tidjani (may ALLAH sanctify his precious secret) addressed to his disciple Sheikh el Islam Ibrahim Riyahi (may ALLAH be pleased with him).
“I give you my permission and authorization for the whole of the noble, blessed and vast wird, pay attention at to all that follows.
Waken your soul (Nafs) from heedlessness and do not comply with its debauchery because this matter is not futile, it is serious and important.
Follow the path of great effort, because punishments are harsh and miseries are many for the poor person who renounces his pact. Be sure of what you have, do not neglect what you have attained […]. Our Tariqa has been singled out by ALLAH with a specificity which places it above all other paths, words are insufficient to shed light on its truth. Only he who has been accepted by ALLAH’s grace can take refuge in this path. If ever the veil that conceals it was lifted, the great poles would have yearned for it like the shepherd in the desert yearns for the clouds.
Take care! Look straight ahead, do not be misled because all spiritual paths come from it. It is the source of all Turuq since the beginning of creation and until the blow of the trumpet on the Day of Judgement, as truly promised by the Master of Existence (peace and blessings be upon him).
I authorize (this) completely and entirely for all time without further modification, on the obligatory condition that you forsake all visits to the saints, with the sole exception of the visit to the Prophet (peace and blessings be upon him) and his companions (may ALLAH be pleased with them).
Know that ALLAH, through His immense Kindness, has graced us with the gift of the prayer known as Djaouharatou-l-Kamel, because for whoever recites it twelve times with complete ablutions and says: “This is a gift for you, O Messenger of ALLAH” it is equivalent to visiting the Prophet (peace and blessings be upon him) in his “heavenly garden” (rawda sherifa) and visiting all the awliya (holy men of God), since the Prophet (peace and blessings be upon him)’s exile until the accomplishment of this zikr.
Notice, may ALLAH have mercy upon you, these great favors, these gems of great worth that ALLAH The Generous has given us, and of which all other peoples have been deprived.
Our Tariqa is hidden from all but the Master of Existence (peace and blessings be upon him) who knows it and knows its worth. May ALLAH establish us and you also, among those who hold tightly to it and those who follow its path in life and in death, in peace, good health and security until we are established in the highest degrees of Paradise near to the Master of Existence (peace and blessings be upon him).
Beware and take heed! Refrain from laziness, from shame and from neglecting what we have ordered you to do, and from staying in the place of doubt and error (going astray). I advise you to fear ALLAH both interiorly and exteriorly and to follow the Sunna however far, however near, however exceptional in words and deeds, to be satisfied with ALLAH whether little or lots, to go towards ALLAH and pay attention to Him in all situation (inner states), to detach yourself from all creatures, whether you are close to them or far from them, and to take the Sunnah as judge in all situation.
I recommend uprightness in all circumstances, in movement as in immobility, I advise patience and complete surrender to ALLAH on the condition that you abandon all that is not righteous. Patience in difficult times is close to peace. Praise Him for His blessings and request Him to grant you the straight path and all good, to take care of you as he has taken care of the elite among his beloved servants, those of high rank, the true ones (Siddiquiyya el ‘Adhma) and those of great sainthood, by the intermediary of the Chosen’s worth (peace and blessings be upon him), and may He take you under His care, may He suffice you, may He take you under His protection, may He immunize you against evil.”