From Aboo Hurairah – radiyallaahi ‘anhu – who said: Allaah’s Messenger – salallaahu ‘alayhi wa sallam – said:
<<Among the deeds and virtues whose reward will reach the Believer after his death are: knowledge that he taught and disseminated; a righteous son whom he left behind; a written copy of the Qur`aan which he left as a legacy; or a mosque that he built; or a house that he built for the passing traveller; or a canal which he dug and caused to flow; or charity which he gave from his property whilst he was alive and well, for which he will continue to receive reward after his death.>>
Reported by Ibn Maajah (no.242), Ibn Khuzaymah (4/121/2490), and al-Bayhaqee in Shu`abul-Eemaan (3/274/3448). Declared ‘hasan’ by Shaikh al-Albaanee in Saheehut- Targheeb wat-Tarheeb (no.77).
Source: http://alitisaambissunnah.wordpress.com (It has Arabic text of hadeeth as well)