How does a Muslim maintain purity of heart with his brothers and friends?
Yes. Holding fast to his religion— the whole religion—is good.
It enjoins good: he should hold fast to his religion.
And he should not heed anyone who wants him to let go of religion.
or makes wrongdoing attractive to him, or makes division attractive to him.
He should pay no attention to that, for that comes from corrupters on earth.
Allah ﷻ warned us against those who call to misguidance.
We must heed what Allah ﷻ said.
“And hold fast to the Rope of Allah all together, and do not be divided.”
The Rope of Allah is the Quran, Islam, and the Messenger ﷺ.
All of them together— not one or two.
All together, the whole ummah. Yes.