If the the neighbour is in need and requires simple assistance, then it is encouraged to be at his assistance, in fact, at times it may be mandatory upon him to help.
On the authority of Anas bin Malik, may Allah be pleased with him, that the Prophet sallahu alayhi wa salam, said:
ما آمن بي من بات شبعانا وجاره جائع إلى جنبه وهو يعلم به
[The one who sleeps with a full stomach knowing that his neighbour is hungry, doesn’t believe in me.]
Reported by al-Bazaar and at-Tabaraanee.
And another wording is:
ليس المؤمن الذي يشبع وجاره جائع إلى جنبه
[A man is not a believer; who fills his stomach while his neighbour is hungry]
Authenticated by al-Imam Albany rahimahullah in his book Saheeh al-Jaami #5505.
Allah, The Most High, says:
﴿وَيَمْنَعُونَ الْمَاعُونَ ﴾
(And they withhold Al-Ma`un i.e simple assistance .) [107:7].
Al-Imaam Ibn Katheer, rahimahullah, commented on this verse by saying:
“…They do not even lend that which others may benefit from and be helped by…”
An excerpt from the abridged english version of tafseer ibn Katheer.
*As a side note: Al-Ma`un is what the people give to each other. For example an axe, a pot, a bucket, and similar items.
Ash-Shaykh Muhammad bin Saalih al-Uthaymeen, rahimahullah, said:
فيجب الإحسان إليهم بقدر الإمكان ، ويحرم الاعتداء عليهم بأي عدوان ، وفي الحديث عن النبي صلى الله عليه وسلم أنه قال : (( من كان يؤمن بالله واليوم الآخر فليحسن إلى جاره ))
“…It is compulsory to show goodness towards them (i.e. the neighbours) according to what is within one’s capability and it is haraam to transgress them with any form of oppression. And in the hadeeth, the Prophet sallahu alayhi wa salam, said: “Whosoever believes in Allah and in the Last Day then let him be good to his neighbour”
Reference : http://islamport.com/w/srh/Web/2365/365.htm
The Mufti, Ash-Shaykh Abdul-Azeez AaliShaykh, may Allah preserve him, said:
إن رأيته فقيرا معوزا فأحسن إليه على قدر استطاعتك،
“… And if you see that he is poor and in need then, show goodness towards him according to what is within your capability… ”
Reference : http://www.mufti.af.org.sa/node/2760
Ash-Shaykh Saalih al-Fawzaan, may Allah preserve him, said:
الجار يحسن إليه ولا يساء إليه، ولو كان كافرا؛
“…One should be good to his neighbour and he shouldn’t be bad to him even if he is a disbeliever…”
Translated by Abu Fajr Abdulfattah
Reference : http://islamport.com/d/2/ftw/1/6/340.html