In The Name of Allaah, The Most merciful, The Bestower of Mercy.
Allaah [The Most High] said:
فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍ مِّنْهُمْ طَائِفَةٌ لِّيَتَفَقَّهُوا فِي الدِّينِ وَلِيُنذِرُوا قَوْمَهُمْ إِذَا رَجَعُوا إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ
Of every troop of them, a party only should go forth, that they (who are left behind) may get instructions in (Islamic) religion, and that they may warn their people when they return to them, so that they may beware (of evil). [Surah at-Tawbah’ Aayah 122]
This Aayah has been explained in two ways, the first meaning is that not all the people should go forth [i.e. travel] to seek knowledge, otherwise everyone will abandon the beneficial [necessities] of the worldly life. Therefore, a group is to preoccupy themselves with the beneficial [necessities] of the worldly life and another group goes forth [i.e. travel] to seek knowledge, then they return to their people to teach them what they have learnt from the religion of Allaah- knowledge of the divine revelation which Muhammad [sallal laahu alayhi wasallam] was sent with. It has been transmitted in a hadeeth reported by Maalik Ibn Huwayrith that a group amongst his people went to the Prophet [sallal laahu alayhi wasallam] and stayed with him for twenty days and nights…hadeeth as follows:
Narrated Maalik [radiyallaahu-anhu]: we came to the Prophet [sallal-laahu-alayhi-wasallam] and stayed with him for twenty days and nights. We were all young and of about the same age. The Prophet [sallal-laahu-alayhi-wasallam] was very kind and merciful. When he realised our longing for our families, he asked about our homes and the people there, and we told him. Then he asked us to go back to our families and stay with them and teach them [the religion and to order them to do good things…. [Saheeh al-Bukhaari’ Number 631]
[An Excerpt from ‘Marhaban Yaa Taalibal Ilm’ pages 128-129. slightly paraphrased]