1. A tale-teller can never be a truthful person

Hujjat-ul-Islam Sayyiduna Imam Muhammad Ghazali رَحْمَةُ اللهِ تَعَالٰی عَلَيْه has narrated: Sayyiduna Imam Muhammad Bin Shihaab Zuhri رَحْمَةُ اللهِ تَعَالٰی عَلَيْه was once sitting with the king, Sulayman Bin Abdul Malik. In the meanwhile, a person came. In an unpleasant manner, the king said to him, ‘I came to know that you have said such and such a thing about me.’ He replied, ‘I never said any such thing.’ The king persistently said, ‘The one who has told me, (how can he lie?) He is a very truthful person.’ Sayyiduna Imam Zuhri رَحْمَةُ اللهِ تَعَالٰی عَلَيْه addressed the king and said, ‘(The one who gave you this news is a tale-teller and) a tale-teller can never be truthful.’ Listening to this, the king calmed down and said:  ‘Your Highness! You are absolutely right.’ Then the king said to that person: ‘اِذْھَبْ بِسَلَامٍ’ i.e. return with peace. (Ihya-ul-‘Uloom, vol. 3, pp. 193)

2. The way of Sayyiduna ‘Umar Bin ‘Abdul ‘Azeez

A person came in the court of Ameer-ul-Mu`mineen Sayyiduna ‘Umar          Bin ‘Abdul ‘Azeez رَحْمَةُ اللهِ تَعَالٰی عَلَيْه and said something negative about someone.  He رَحْمَةُ اللهِ تَعَالٰی عَلَيْه said: If you want, I can investigate in this matter (what you said). If you are found to be a liar, then you will be subjected to under the following Ayah:

اِنْ جَآءَكُمْ فَاسِقٌۢ بِنَبَاٍ فَتَبَیَّنُوْۤا

If any sinner brings you some news, so (you must) investigate it.

[Kanz-ul-Iman (Translation of Quran)] (Part 26, Surah Al-Hujurat, Ayah 6)

And if you are found to be truthful, then you will come under the ruling of the following Ayah:

هَمَّازٍ مَّشَّآءٍۭ بِنَمِیْمٍۙ(۱۱)

The excessive slanderer, going about excessive slandering.

[Kanz-ul-Iman (Translation of Quran)] (Part 29, Surah Al-Qalam, Ayah 11)