Friends of Prophet Abdullah bin Abbas radhiyallahu anhuma stated:

إنا كنا مرة إذا سمعنا رجلا يقول قال رسول الله -صلى الله عليه وسلم- ابتدرته أبصارنا وأصغينا إليه بآذاننا فلما ركب الناس الصعب والذلول لم نأخذ من الناس إلا ما نعرف

We used to hear someone say: The Prophet sallallaahu alaihi wasallam said ... we focused our vision and hearing on him. But when humans have begun to take a difficult and easy path (not selective in receiving knowledge, pent), then we do not take (knowledge) from humans except what we know (the history of Muslims in Muqoddimah Shahih)

Muhammad bin Sirin - one Tabi'i, students from several Companions of the Prophet (pbuh) stated:

إِنَّ هَذَا الْعِلْمَ دِينٌ فَانْظُرُوا عَمَّنْ تَأْخُذُونَ دِينَكُمْ.

Indeed this knowledge is Dien. Then look at you from whom you took (knowledge) of your Dien (Muslim history in Muqoddimah Shahih)

لم يكونوا يسألون عن الإسناد فلما وقعت الفتنة قالوا سموا لنا رجالكم فينظر إلى أهل السنة فيؤخذ حديثهم وينظر إلى أهل البدع فلا يؤخذ حديثهم.

They used to (the Ulama in the Friends) did not ask about sanad. When slander occurs, they say: Name your narrators (hadith). To be seen (whether it comes from) Ahlussunnah, so that the hadith is taken (accepted). And seen (whether it comes from) Ahlul Bid'ah so that their hadith is not taken (the history of Muslims in Muqoddimah Shahih)

Uqbah bin Nafi - a Tabi'i, student of the Companion of the Prophet Ibn Umrahimahullah had an inheritance to his son:

لاَ تَقْبَلُوْا الْحَدِيْثَ عَنْ رَسُوْلِ اللهِ صَلَّى اللهُ عَلَيْهَ وَسَلَّمَ إِلَّا عَنْ ثِقَةٍ

Do not accept the hadith from the Prophet sallallaahu alaihi wasallam except from the person who is tsiqoh (trusted) (Sejarah al-Khothib in al-Kifaayah fi Ilmir Riwaayah, Ibnu Abdil Bar in atTamhiid)

It is reported that Al-Imam Malik - one of the teachers of al-Imam Ash-Shafi'-rahimahullah stated:

إِنَّ هَذَا الْعِلْمَ هُوَ لَحْمُكَ وَدَمُكَ وَعَنْهُ تُسْأَلُ يَوْمَ الْقِيَامَةِ فَانْظُرْ عَنْ مَنْ تَأْخُذُهُ

Indeed this knowledge (religion) is your blood and flesh. You will be asked about that on the Day of Judgment. Therefore, see from whom you take the knowledge (history) (history of arRoomahurmuziy in al-Muhadditsul Faashil)