Allah عَزَّوَجَلَّ has Himself commanded us to keep good company of the pious people. It is stated in verse 119 of Surah At-Taubah, part 11:

یٰۤاَ یُّہَا   الَّذِیۡنَ   اٰمَنُو ا   اتَّقُو ا   اللّٰہَ   وَ کُوۡنُوۡ ا   مَعَ    الصّٰدِ قِیۡنَ   ﴿۱۱۹﴾

Translation from Kanz-ul-Iman: O People who Believe! Fear Allah, and be with the truthful. (Part 11, Surah At-Taubah, verse 119)

It is stated on page 258 of commentary Siraat-ul-Jinaan, volume 4, published by Maktaba-tul-Madinah that this verse gives the evidence of having the company of pious people because one way of being with them is to keep their company. One of the effects of having their company is that we are enabled to abstain from sins and perform good deeds, after observing good character and good deeds. Another effect is that it removes the hardness from the heart and creates softness in the heart. A person is privileged to die with faith and will focus on the serious matters of the grave and Day of Judgment. Therefore, every Muslim should have relationships with the pious people and keep their company and know whose company he is going to have.

Sayyiduna Abu Hurayrah رَضِىَ اللهُ تَعَالٰی عَـنْهُ has narrated that the Beloved Prophet
صَلَّى اللهُ تَعَالٰى عَلَيْهِ وَاٰلِهٖ وَسَلَّم has said: A person is influenced by the faith of his friend. Therefore, he should see with whom he is forming a friendship with.

(Sunan-ut-Tirmizi, vol. 4, pp. 167, Hadees 2385)

Persuading us to find a religious friend, Sayyiduna ‘Umar Farooq رَضِىَ اللهُ تَعَالٰی عَـنْهُ has said, ‘Find true friends and spend your life with them because they are grace in pleasure and necessary in trials. And do not keep the company of a sinner, otherwise you will learn to commit sins from him.

(Ihya-ul-‘Uloom, vol. 2, pp.  214)

Blessings of saying Aameen to the Du’a of a pious person

Be in seclusion to make your world and Hereafter better by performing religious activities and completing your necessary work of the world or keep the company of such Sunnah-practising Islamic brothers whose words become