Advice by the Prophet ﷺ
Sufian al-Thaqafi reported, "I said, 'O Messenger of Allah, tell me about Islam in one word that I would not ask anyone other than you (according to Abu Muʿawiyah he said, "anyone after you").'
The Prophet -peace be upon him- said:
'Say I believe in Allah and then stand steadfast.'"
Musnad Ahmad 14869
 Imām Shāfiʿī on Knowledge:
“Knowledge is not what one has memorized.
Knowledge is what benefits.”
“This Knowledge of ours” -
“Belief in this knowledge of ours is friendship with Allah.
If you have failed to receive the grace within yourself,
then fail not to believe in the grace which others have received.”
 Urgency: (advice by Ibn Masud)
“Search for knowledge while it is to be found.
When those who have it die, it becomes concealed.”
 Among Sahl al-S. uʿlūkī's sayings:
“The approval of people is hard to obtain and unattainable,
but Divine approval is easily within reach and indispensible.”
“Whoever takes up leadership before his time
undertakes his own disgrace.”
 Advice by Muʿādh bin Jabal :
ʿAbdullāh, son of Imam Ahmad bin Hanbal Allah be pleased with him, narrated that a man asked Muʿādh bin Jabal Allah be pleased with him: "Teach me something." Muʿādh replied: "Would you obey me?" The man humbly replied: "I am most eager to obey you." Muʿādh then instructed the man:
"Fast and pray regularly, earn your livelihood in a lawful way, and do not err in that regard. Strive not to die except in Islam, and beware not to become liable before the divine justice regarding the grievance of someone with whom you have dealt unjustly."
 Abdullah Ibn al-Mubarak
 Al-Khatib al-Baghdadi
O student of knowledge, I exhort you to purify your intention in pursuing knowledge and to strive to make your soul act according to knowledge's dictates. For the science is a tree of which deeds are the fruit, and he is not counted learned, who does not put his learning into practice....
And did those of the Salaf of the past reach whatever high levels they reached, other than by purified beliefs, righteous deeds, and renouncing most of the refinements of the world? And did the wise people of the past attain greater felicity except through hard work and diligence, contentment with little, and spending of their superfluity to meet the need of the needy and destitute?
Surely, he who gathers books of knowledge
is no different than he who gathers gold and silver. Surely, the devourer
of books is no different from the greedy miser. Surely, the bibliophile
enamoured with books is no different from the hoarder of gold and silver.
Therefore, just as wealth does not benefit except through its spending,
likewise do the sciences not benefit except those who put them into
practice and observes their requirements.
see: Al-Khatib al-Baghdadi
 Ibn `Arabi's advice for the traveler
Know (may Allah grant success to us both) that if you want to enter the presence of the Truth and receive from Him without intermediary, and you desire intimacy with Him, this will not be appropriate as long as your heart acknowledges any lordship other than His. For you belong to that which exercises its authority over you. Of this there is no doubt. JLP29
 Counsel Sidi Ahmad Zarrooq
Know that repentance is a key. And Taqwaa [awareness of Allah] is vast. And Uprightness is the source of rectification. Furthermore a servant is never free of either blunders, or shortcomings, or lassitude. Therefore never be neglectful of Tawbah [repentance], and never turn away from the act of returning to Allah (SubHana Wa Taʿala ), and never neglect acts that bring you closer to Allah (SubHana Wa Taʿala ). Indeed, every time one of these three occurs, repent and return.
Every time that you make a mistake, listen and obey. Any time you display shortcoming or lack of enthusiasm, don't desist in your efforts. Let your main concern be to remove from your outer state anything that is displeasing, and then maintain its outward state from continuous counsel. Continue doing this until you find that your fleeing from anything outwardly displeasing is second nature, and your avoidance of the boundaries of prohibited things is as if it acts like a protective net that is placed before you. At this point, it is time to turn inward, toward your heart's presence, and to its reality with both reflection and remembrance. Don't hasten the end result before you have completed the beginning. But likewise, don't begin without looking toward the end result. This is so because the one who seeks the outset at the end loses providential care; and the one who seeks the end at the outset loses providential guidance.
Act in accordance with principles and the appropriate legal
rulings, and not in accordance with stories and fantasies...
Organize your time in a manner appropriate to the time-specific
needs using gentleness and toleration. And be very wary of either
harshness or laxity. This is so because too much laxity concerning
permissible matters pulls the heart backward in its journey, until
even a man of resolve ends up looking like a foolish boy...
Counsel Sidi Ahmad Zarrooq
If you pray and feel satisfaction at having prayed, your action
has made you worse. In such circumstances, wait* to pray until
you have learned how to be really humble.
Adapted from Sayed Sultan, * original has instead of 'wait': 'cease to pray,' TE-120
Never rely upon what you believe to be inner experiences because
it is only when you get beyond them that you will reach knowledge.
They are there to deceive you.
Counsels of Bahaudin, TE-187
You should try to devote yourself to worship nicely, so as to receive enjoyment from your supplication and recitation of the Holy Quran. If you succeed in this your heart will automatically become indifferent to the people and their acquaintance and contacts, and you shall become disgusted with them. MHA88