اتَّخَذُواْ أَحْبَارَهُمْ وَرُهْبَانَهُمْ أَرْبَابًا مِّن دُونِ اللّهِ وَالْمَسِيحَ ابْنَ مَرْيَمَ
They took their rabbis and their monks to be their lords besides Allah, and the Messiah, son of Maryam.
Imam Ahmad, At-Tirmidhi and Ibn Jarir At-Tabari recorded a Hadith via several chains of narration, from Adi bin Hatim, may Allah be pleased with him, who became Christian during the time of Jahiliyyah. When the call of the Messenger of Allah reached his area, Adi ran away to Ash-Sham, and his sister and several of his people were captured.
The Messenger of Allah freed his sister and gave her gifts. So she went to her brother and encouraged him to become Muslim and to go to the Messenger of Allah. Adi, who was one of the chiefs of his people (the tribe of Tai') and whose father, Hatim At-Ta'i, was known for his generosity, went to Al-Madinah. When the people announced his arrival, Adi went to the Messenger of Allah wearing a silver cross around his neck. The Messenger of Allah recited this Ayah;
اتَّخَذُواْ أَحْبَارَهُمْ وَرُهْبَانَهُمْ أَرْبَابًا مِّن دُونِ اللّهِ
They took their rabbis and their monks to be their lords besides Allah.
Adi commented, "I said, `They did not worship them."'
The Prophet said,
بَلَى إِنَّهُمْ حَرَّمُوا عَلَيْهِمُ الْحَلَلَ وَأَحَلُّوا لَهُمُ الْحَرَامَ فَاتَّبَعُوهُمْ فَذَلِكَ عِبَادَتُهُمْ إِيَّاهُم
Yes they did. They (rabbis and monks) prohibited the allowed for them (Christians and Jews) and allowed the prohibited, and they obeyed them. This is how they worshipped them.
The Messenger of Allah said to Adi,
يَا عَدِيُّ مَا تَقُولُ
O Adi what do you say?
أَيُفِرُّكَ أَنْ يُقَالَ اللهُ أَكْبَرَ
Did you run away (to Ash-Sham) so that 'Allahu Akbar' (Allah is the Great) is not pronounced?
فَهَلْ تَعْلَمُ شَيْيًا أَكْبَرَ مِنَ الله
Do you know of anything greater than Allah?
مَا يُفِرُّك
What made you run away?
أَيُفِرُّكَ أَنْ يُقَالَ لَا إِلَهَ إِلاَّ اللهُ
Did you run away so that `La ilaha illallah' is not pronounced?
فَهَلْ تَعْلَمُ مَنْ إِلهٌ إِلاَّ اللهُ
Do you know of any deity worthy of worship except Allah?
The Messenger invited Adi to embrace Islam, and he embraced Islam and pronounced the Testimony of Truth. The face of the Messenger of Allah beamed with pleasure and he said to Adi,
إِنَّ الْيَهُودَ مَغْضُوبٌ عَلَيْهِمْ وَالنَّصَارَى ضَالُّون
Verily, the Jews have earned the anger (of Allah) and the Christians are misguided.
Hudhayfah bin Al-Yaman, Abdullah bin Abbas and several others said about the explanation of,
اتَّخَذُواْ أَحْبَارَهُمْ وَرُهْبَانَهُمْ أَرْبَابًا مِّن دُونِ اللّهِ
(They took their rabbis and their monks to be their lords besides Allah...),
that the Christians and Jews obeyed their monks and rabbis in whatever they allowed or prohibited for them.
This is why Allah said,
وَمَا أُمِرُواْ إِلاَّ لِيَعْبُدُواْ إِلَـهًا وَاحِدًا
while they were commanded to worship none but One God,
Who, whatever He renders prohibited is the prohibited, whatever He allowed is the allowed, whatever He legislates, is to be the law followed, and whatever He decides is to be adhered to;
لااَّ إِلَـهَ إِلااَّ هُوَ سُبْحَانَهُ عَمَّا يُشْرِكُونَ
None has the right to be worshipped but He. Hallowed be He above what they associate (with Him).
Meaning, exalted, sanctified, hallowed above partners, equals, aids, rivals or children, there is no deity or Lord worthy of worship except Him