The Holy Prophet (S) said: "Man is influenced by the faith of his friends. Therefore, be careful of whom you associate with."
Bihar-ul-Anwar, vol. 74, p. 192
Imam as-Sadiq (‘a) said: "Be the friend of he who may grace you, not of one whom you are better than." (- viz. make friends with ones who are higher than you so that you progress.)
Bihar-ul-Anwar, vol. 76, p. 267
Imam as-Sadiq (‘a) said: "My most beloved brother is he who (makes me aware of) my faults."
Bihar-ul-Anwar, vol. 74, p. 282
Imam Amir-ul-Mu'mineen ‘Ali (‘a) said: "Verily, there are three (types of) friends for a Muslim:
1. The friend who says: 'I am with you whether you are alive or dead', and this is his deed.
2. The friend who says: ' I am with you unto the threshold of your grave and then I will leave you', and this is his child.
3. The friend who says: 'I will be with you until when you die', and this is his wealth which will belong to the inheritors when he dies."
From this tradition, and the like, we understand that the only thing which will avail for individuals in the Hereafter is Faith and good deeds. This is also referred to in many Islamic traditions as well as the verses of the Holy Qur'an, for example:
"For those who believe and work righteousness is (every) blessedness and a beautiful place of (final) return." (13:29)
"As to those who believe and work righteousness, verily We shall not suffer to perish the reward of any who do a (single) righteous deed." (18:30)
"As to those who believe and work righteous deeds, they have, for their entertainment, the Gardens of Paradise." (18: 107)
"On those who believe and work deeds of righteousness, will (God) Most Gracious bestow Love." (19:96)
Al-Khisal by Saduq, vol. 1, p. 88
Imam as-Sadiq (‘a) said: "Be careful to have truthful friends and try to obtain them, for they are your support when you are in welfare, and your advocator when you have misfortune.
Bihar-ul-Anwar, vol. 74, p. 187
Imam Sajjad (‘a) said: "The meeting of the righteous invites you to goodness."
Bihar-ul-Anwar, vol. 78, p.141
Imam Sajjad (‘a) said: "Beware of the companionship of the sinful, and helping of the unjust."
Bihar-ul-Anwar, vol. 78, p.151.