A labourer can give charity out of his earnings and it is severely forbidden to detract on who contributes a little

598. Narrated Aboo Mas’ood (radhi Allaahu anhu) :

When we were ordered to give alms, we used to start to work as porters (to earn something we could give in charity). Aboo ‘Uqail came with one half of a Saa (special measure for food grains) and another person brought more than he did. So the hypocrites said, “Allaah is not in need of the alms of this (i.e. ‘Uqail); and this other person did not give alms but for showing off.” Then Allaah (Subhahanu wata’alaa) revealed : ‘Those who defame such of the believer who give charity (in Allaah’s Cause) voluntarily, and those who could not find to give charity (in Allaah’s Cause) except what is available to them…’ (V.9 : 79)

[Saheeh Al-Bukhaari, Hadeeth No. 190, Vol. 6]

Source : The Book Of Zakat : Chapter 21 – A labourer can give charity out of  his earnings and it is severely forbidden to detract on who contributes a little. Al-Lulu Wal-Marjan, Compiled by : Fuwad Abdul-Baqi, Translated by : Dr. Muhammad Muhsin Khan