The Virtue of calling Others to Allah
Allah says,
وَمَنْ أَحْسَنُ قَوْلاً مِّمَّن دَعَا إِلَى اللَّهِ
And who is better in speech than he who invites to Allah,
means, he calls the servants of Allah to Him.
وَعَمِلَ صَالِحًا وَقَالَ إِنَّنِي مِنَ الْمُسْلِمِينَ
and does righteous deeds, and says;"I am one of the Muslims."
means, he himself follows that which he says, so it benefits him as well as others. He is not one of those who enjoin good but do not do it themselves, or who forbid evil yet they do it themselves. He does good and avoids doing evil, and he calls people to their Creator, may He be blessed and exalted.
This is general in meaning and applies to everyone who calls people to what is good and is himself guided by what he says. The Messenger of Allah is the foremost among people in this regard, as Muhammad bin Sirin, As-Suddi and Abdur-Rahman bin Zayd bin Aslam said.
It was also said that what was meant here is the righteous Mu'adhdhin, as it was mentioned in Sahih Muslim;
الْمُوَذِّنُونَ أَطْوَلُ النَّاسِ أَعْنَاقًا يَوْمَ الْقِيَامَة
The Mu'adhdhins will be the ones with the longest necks on the Day of Resurrection."
In As-Sunan it is reported that the Prophet said;
الاِْمَامُ ضَامِنٌ وَالْمُوَذِّنُ مُوْتَمَنٌ فَأَرْشَدَ اللهُ الاَْيِمَّةَ وَغَفَرَ لِلْمُوَذِّنِين
The Imam is a guarantor and the Mu'adhdhin is in a position of trust. May Allah guide the Imams and forgive the Mu'adhdhin."
The correct view is that the Ayah is general in meaning, and includes the Mu'adhdhin and others. When this Ayah was revealed, the Adhan had not been prescribed at all. The Ayah was revealed in Makkah, and the Adhan was prescribed in Al-Madinah after the Hijrah, when it was shown to Abdullah bin Abd Rabbihi Al-Ansari in a dream. He told the Messenger of Allah about it, and he told him to teach it to Bilal, may Allah be pleased with him, who had a more beautiful voice, as we have discussed elsewhere.
So the correct view is that the Ayah is general in meaning, as Abdur-Razzaq said, narrating from Ma`mar, from Al-Hasan Al-Basri, who recited this Ayah;
وَمَنْ أَحْسَنُ قَوْلاً مِّمَّن دَعَا إِلَى اللَّهِ وَعَمِلَ صَالِحًا وَقَالَ إِنَّنِي مِنَ الْمُسْلِمِينَ
And who is better in speech than he who invites to Allah, and does righteous deeds, and says;"I am one of the Muslims." and said,
"This is the beloved of Allah, this is the close friend of Allah, this is the chosen one of Allah, this is the most beloved of the all the people of earth to Allah. He responded to the call of Allah and called mankind to that to which he had responded. He did righteous deeds in response and said, `I am one of the Muslims.'
This is Allah's Khalifah."
Wisdom in Da`wah etc.
Allah says,