It is wise to choose moderation in dealing with friends. Excessive love and confidence in friends are unacceptable since it happens that a friend may change into an enemy and use the secrets that he had shown as weapons.

Imam Ali (a) said: “When you cherish someone you should cherish him moderately for he may be your enemy someday, and when you hate someone you should hate him moderately for he may be your friend someday.” (18)
Imam as-Sadiq (a): “The secrets that you must show before your friends are only those through which your enemies cannot harm you, for a friend may change into an enemy.”
1. Quoted from Bihar ul-Anwar; Kitab ul-Ashara; 51 (as quoted from al-Amali).

2. Quoted from al-Wafi; part 3 page 104 (as quoted from al-Kafi).

3. Quoted from al-Wafi; part 3 page 104 (as quoted from al-Kafi).

4. Quoted from Bihar ul-Anwar; Kitab ul-Ashara 56 (as quoted from al-Kafi).

5. Quoted from Bihar ul-Anwar; Kitab ul-Ashara; 52 (as quoted from al-Amali).

6. Quoted from Bihar ul-Anwar; Kitab ul-Ashara; 53 (as quoted from Sifat ush-Shia).

7. Quoted from al-Wafi; part 3 page 105 (as quoted from al-Kafi).

8. Quoted from Nahj ul-Balagha.

9. Quoted from al-Wafi; part 3 page 106 (as quoted from al-Kafi).

10. Quoted from Bihar ul-Anwar; Kitab ul-Ashara page 46 (as quoted from al-Amali).

11. Quoted from Bihar ul-Anwar; Kitab ul-Ashara; 46 (as quoted from Qadhaa ul-Huqouq).

12. Quoted from Bihar ul-Anwar; Kitab ul-Ashara 56 as quoted from al-Kafi.

13. Quoted from Nahj ul-Balagha.

14. Quoted from Nahj ul-Balagha: Imam Ali’s commandment for Imam al-Hasan.
15. Quoted from Tuhaf ul-Uqoul.16. Quoted from al-Wafi; part 3 page 86 (as quoted from al-Kafi).
17. Quoted from Sheikh as-Saduq’s Meaani al-Akhbar.18. Quoted from Nahj ul-Balagha.

Source: tebyan