Hawzah News Agency – Imam al-Sadiq peace be upon him says:

لا تَكونُ الصَّداقَةُ إلّا بِحُدُودِها، فَمَن كانَت فيهِ هذهِ الحُدودُ أو شَي‏ءٌ مِنهُ، وإلّا فلا تَنسِبْهُ إلى‏ شَي‏ءٍ مِن الصَّداقَةِ، فَأوَّلُها: أن تكونَ سَرِيرَتُهُ وعَلانِيَتُهُ لكَ واحِدَةً، والثانيةُ: أن يَرى‏ زَينَكَ زَينَهُ، وشَينَكَ شَينَهُ، والثالثةُ: أن لا تُغَيِّرَهُ علَيكَ وِلايَةٌ ولا مالٌ، والرابعةُ: لا يَمنَعُكَ شَيئاً تَنالُهُ مَقدُرَتُهُ، والخامسةُ - وهي تَجمَعُ هذهِ الخِصالَ - : أن لا يُسلِمَكَ عِندَ النَّكَباتِ.

 ‘Friendship can only succeed when its conditions are fulfilled, and he who fulfils all or some of these conditions may be befriended, and if not, then do not attribute any of your friendship to him. The first of these conditions is that he should treat you in public the same as he treats you in private. Secondly, that your source of pride is a source of pride for him, and your source of shame is a source of shame for him too. Thirdly, that neither position nor wealth should change him towards you. Fourthly, that he must not prevent you from obtaining that which you have the capacity for, and fifthly – and this sums up all the other qualities – that he must not give up on you in times of misfortune.’

Source: Bihar al-Anwar, v. 78, p. 249, no. 90