“The best of people is the one who is most useful to other people.” 
According to reports, he also said:
“The best of mujāhids on the path of Allāh is the one who serves them.” 
Because the honourable companions (ashāb) were aware of the honour of hizmat, the most virtuous of them would ask to be given the task of serving the others. If they were unable to obtain this, they would ask to be allowed to serve as mu’azzin (one who recites the azān).
The hizmat done to people is superior to nāfila/nafl ibādats. We only need to remember the following hadīs on this issue:
“It is more beloved to me that I walk to meet the needs of a mu’min brother than to enter i’tikāf (seclusion) in this masjid (Masjid-i Nabawī) for one month.” 
“For as long as a person helps one of his brothers in dīn, Allāh helps him.” 
One of the companions, Abdullāh bin Abbās (RA), entered i’tikāf at the masjid of our beloved prophet (SAW). A man approached him, greeted him and sat. Ibn Abbās (RA) looked at the man’s face, observed that he was a little sad, and said:
“O such-and-such! You seem sad and unhappy; are you troubled by something?”
“Yes, O cousin of Allah’s Messenger, such-and-such a person has rights over me because they granted me my freedom in return for money. But, by the rights of the Prophet lying in this rawda: I can not afford to pay the debt I have undertaken!”
Ibn Abbas (r.a.) asked, “May I talk to him about you?”
The man replied, “Talk if you wish.”
Ibn Abbās (RA) immediately put on his shoes and left the masjid. The man said: “You seem to have forgotten that you are in i’tikāf!”
Ibn Abbās (RA) replied, “No, I haven’t forgotten, but I heard the voice of our beloved prophet (SAW) lying in his grave. It has not been long since he left us,” and tears began to come from Ibn Abbās’ eyes. Then he continued:
“Our beloved Rasūlullāh told us the following:
“Whoever walks to meet the need of his brother in dīn and removes his troubles, this is better for him than ten years of i’tikāf. And yet whoever enters i’tikāf for a single day for the sake of Allāh Ta’ālā’s pleasure, Allāh puts three trenches between this person and Jahannam. The distance between each trench is equal to the distance between east and west.” 
 Ali al-Müttakî, Kanzü’l-Ummal, nr., 16519. For a short narration on the subject see Saîd b. Mansûr, Sünen, nr. 2406; Ibnü’n-Nehhâs, Meshâriu’l-Eshwâk, 1/314.
 Taberânî, al-Awsât, nr., 7583; Münavî, Künüzü’l-Hakâik, nr., 3512.
 Tirmidhî, Jihad, 5; Ahmed, Müsned, 5/270; Hâkim, Müstedrek, 2/91.
 Tabarânî, al-Awsat, nr.4990; Süyûtî, as-Sagîr, nr.1286; Haysamî, az-Zavâid, 5/290.
 Tabarânî, a l – K a b î r, nr. 13646; Ibn Abü’d-Dünya, K a z â ü ’ l – H â j e, nr. 36.
 Abû Dawud, Edeb, 60; Tirmidhî, Hudûd, 3; Birr, 19.