You must give good advice to all Muslims.
The highest point of this is that you conceal nothing from them which if made known would result in good or preserve from something evil. The Prophet (peace and blessings of Allah be upon him) has said: "Religion is good counsel" part of this is to support a Muslim in his absence as you would in his presence, and not to give him more verbal signs of affection than you have for him in your heart. It is also part of this that when a Muslim asks you for advice, and you know that the correct course does not lie in that which he is inclined to do, you should tell him so.
The absence of good counsel is indicated by the presence of envy of the favors God has given other Muslims. The origin of such envy is that you find it intolerable that God has granted one of his servants a good thing whether of the religion, or of the world. The utmost limit is to wish that he be deprived of it. It has been handed down that "envy consumes good deeds just as fire consumes dry wood". The envious man is objecting to God's management of his dominion, as if to say "O lord! You have put your favors where they do not belong."
It is permitted to be envious without rancor whereby when you see a favor being bestowed on one of his servants, you ask him to grant you the like.
When someone praises you, you must feel dislike for his praises within your heart. If he has praised you for something you truly possess, say: "praise belongs to God who has revealed the good things and hidden the ugly things." and if he praises you for something you do not possess, say "o God! Do not call me to account for what they say, forgive me what they do not know, and make me better than they think."
Do not praise anyone unnecessarily.
When you wish to give advice to someone regarding any behavior of his that you have come to know about, be gentle, talk to him in private and do not express explicitly what may be conveyed implicitly. Should he ask you to tell him who told you that which you know, do not tell him lest it stir up enmity. If he accepts your advice, praise God, and thank him. If he should refuse, blame yourself.
If you are given something as a trust, you have to guard it better than if it was yours. Return that which was entrusted to you, and beware of betraying trust. The Prophet (peace and blessings of Allah be upon him) said:
"He who cannot keep a trust has no faith" and "three things are attached to the throne of God: benefaction which says "o God! I am by you, therefore let me not be denied!" kinship, which says "o God! I am by you, thus let me not be severed!" and trust, which says "o God! I am by you, so let me not be betrayed!"
Speak truthfully and honor commitments and your promises, for breaching them are signs of hypocrisy.
"The signs of a hypocrite are three: when he speaks he lies, when he promises he breaks his promise, and when he is trusted, he betrays that trust."
Beware of arguments and wrangling, for they cast rancor into the breasts of men, alienate hearts and lead to enmity and hatred. If anyone argues against you and has right on his side, accept what he says for truth must always be followed. If on the other hand he is wrong, leave him, for he is ignorant, and God has said "and turn away from the ignorant." [vii :199]
Renounce all joking, if very occasionally you do joke to assuage a Muslim's heart, then speak only the truth. The Prophet (peace and blessings of Allah be upon him) has said: "neither argue with your brother nor quarrel, and do not make him a promise and then break it."
respect all Muslims, especially those deserving of merit, such as the scholars, the righteous, the elderly.
Never frighten or alarm a Muslim, never mock or ridicule them, or despise them.
Be humble for humility is the attribute of believers. Beware of pride for God does not like the proud. Those who humble themselves are raised up by God, and those who are proud are abased by him.
There are signs that distinguish the humble from the proud:
"That God may separate the vile from the good" [viii:37].
Signs of humility include a liking for obscurity, dislike of fame, acceptance of truth whether it be from a lowly or noble person, to love the poor, associate with them, to fulfill the rights people have upon you as completely as you can, thank those who fulfill their duties to you, and excuse those who are remiss. Signs of pride include a liking for positions of most dignity when in company, praising oneself, speaking proudly, open haughtiness, arrogance, strutting, and neglecting the rights of others upon you while demanding your rights from them.