The hadeeth that the questioner is referring to is:
It was narrated that Ibn ‘Abbaas (may Allah be pleased with him) said: A Bedouin came to the Prophet (blessings and peace of Allah be upon him) and said, I have seen the new moon tonight. He said, “Do you bear witness that there is no god except Allaah and that Muhammad is the Messenger of Allaah (blessings and peace of Allah be upon him)?” He said, Yes. He said, “Get up, O Bilaal, and announce to the people that they should fast tomorrow.”
Narrated by al-Tirmidhi (691), Abu Dawood (2340), al-Nasaa’i (2112) and Ibn Maajah (1652). The hadeeth is da’eef (weak) and not saheeh. It was classed as weak by al-Nasaa’i, al-Albaani and others.
As the hadeeth is weak, there is no contradiction between it and what we have mentioned about it being essential that the one who sights the moon should be of good character.
Even if we assume that the hadeeth is saheeh, it may be interpreted in several ways, such as:
That the issue with regard to accepting the testimony of the one who has seen the new moon and the issue of determining whether he is trustworthy and of good character is up to the judge to decide. If he is confident, because of his experience with people, that this person who has seen the moon is trustworthy in his testimony, he may accept this testimony from him, even if no one knows him and is able to confirm that he is of good character and trustworthy.
Shaykh al-Albaani (may Allah have mercy on him) said:
So we see from the hadeeth that he instructed Bilaal to announce to the people that they would fast the next day. So the Messenger (blessings and peace of Allah be upon him) was content with the testimony of this man, whom he did not know, on the basis that he bore witness that there is no God but Allah and that Muhammad is the Messenger of Allah, i.e. he knew that he was a Muslim, but he did not check on him any further and he did not try to find out how intelligent and smart he was, as was the case in the first hadeeth in which the witness was ‘Abd-Allah ibn ‘Umar ibn al-Khattaab. Yet despite that he accepted his testimony. This hadeeth makes things easier for people, and what this means is that the judge should be content with the witness as he appears to be, without needing to find people who know this man and can testify that he is of good character, as was the habit of judges since time immemorial. Rather it is sufficient to know that he is a Muslim. This man was a Bedouin of whom the Prophet (blessings and peace of Allah be upon him) had no prior knowledge and he was content that he uttered the Shahaadatayn before him. So he was a Muslim with the same rights and duties as any other, and based on his testimony and the fact that he was a Muslim he said: O Bilaal, announced to the people that they should fast tomorrow.
Al-Ta’laaq ‘ala Kitaab Buloogh al-Maraam, (audio tape), hadeeth 5, Kitaab al-Siyaam.
That this hadeeth is evidence for the principle that a Muslim is to be regarded as being of good character unless proven otherwise. Al-San’aani (may Allah have mercy on him) said concerning what we learn from the hadeeth of Ibn ‘Abbaas:
It indicates that the basic principle with regard to the Muslims is that they are of good character, because the Prophet (blessings and peace of Allah be upon him) did not ask the Bedouin for anything except the Shahaadah.
Subul al-Salaam by al-San’aani, 2/153
That this ruling only applies to the Sahaabah, which is the case because they are all to be regarded as being of good character. There is no doubt that that Bedouin is to be included as one of the Sahaabah (may Allah be pleased with them), and thus he is to be regarded as a man of good character, one of those who do not need to be examined to prove that they are of good character.
Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allah have mercy on him) said:
All of the Sahaabah are trustworthy and of good character, and the narration of any of them is to be accepted even if he is not known by name. Hence they said: Not knowing the name of the Sahaabi does not affect the validity of the hadeeth.
The evidence for what we have said about the Sahaabah is that Allah and His Messenger praised them in a number of texts, and the Prophet (blessings and peace of Allah be upon him) would accept the testimony of any of them once he knew that he was Muslim, and he would not enquire any further about him. It was narrated that Ibn ‘Abbaas (may Allah be pleased with him) said: A Bedouin came to the Prophet (blessings and peace of Allah be upon him) and said: I have seen the new moon, meaning Ramadan.
End quote from Mustalah al-Hadeeth, from his website.
There is something else that supports what we have stated above, which is the fact that this testimony came at the time of Revelation, and the testimony of the Bedouin could not have been accepted if it was a false testimony concerning one of the acts of worship of the Muslims.
But as the hadeeth is da’eef (weak) there is no need to discuss its meaning. Praise be to Allah the Lord of the Worlds.
And Allah knows best.