Conditions of righteous deeds
Question

What are the conditions which must be met for a deed to be righteous?
Praise be to Allah.Shaykh al-Shanqeeti said:
What is meant in the aayah
“…who do righteous deeds…”
[al-Kahf 18:2 – interpretation of the meaning]
 is explained in other aayahs which indicate that a deed cannot be righteous unless it meets three conditions:
1 – It must be done in accordance with that which was brought by the Prophet (peace and blessings of Allah be upon him). Every action that goes against that which was brought by the Prophet (peace and blessings of Allah be upon him) is not righteous, rather it is false. Allah says (interpretation of the meaning):
“And whatsoever the Messenger (Muhammad) gives you, take it” [al-Hashr 59:7]
“He who obeys the Messenger (Muhammad), has indeed obeyed Allah” [al-Nisa’ 4:10]
“Or have they partners with Allah (false gods) who have instituted for them a religion which Allah has not ordained?” [al-Shoora 42:21]
and there are many similar aayahs.
2 – The one who does it must be sincere in his intention towards Allah. Allah says (interpretation of the meanings):
“And they were commanded not, but that they should worship Allah, and worship none but Him Alone (abstaining from ascribing partners to Him)” al-Bayyinah :5]
“Say (O Muhammad): ‘Verily, I am commanded to worship Allah (Alone) by obeying Him and doing religious deeds sincerely for His sake only.
And I am commanded (this) in order that I may be the first of those who submit themselves to Allah (in Islam) as Muslims.’
Say (O Muhammad): ‘Verily, if I disobey my Lord, I am afraid of the torment of a great Day.’
Say (O Muhammad): ‘Allah Alone I worship by doing religious deeds sincerely for His sake only (and not to show off, and not to set up rivals with Him in worship).’
So worship what you like besides Him’” [al-Zumar 39:11-15]
and there are many similar aayahs.
3 – It must be done on the basis of faith and sound belief, because the action is the roof and the belief (‘aqeedah) is the foundation. Allah says (interpretation of the meaning):
“Whoever works righteousness — whether male or female — while he (or she) is a true believer…”
[al-Nahl 16:97]
So faith is described as the prerequisite for that.
The concept of this prerequisite is explained in many places, such as when Allah describes the actions of non-believers:
“And We shall turn to whatever deeds they (disbelievers, polytheists, sinners) did, and We shall make such deeds as scattered floating particles of dust” [al-Furqaan 25:23]
“their [disbelievers’] deeds are like a mirage in a desert” [al-Noor 24:39]
“their [disbelievers’]works are as ashes, on which the wind blows furiously on a stormy day” [Ibraaheem 14:18] 
and there are many similar aayahs as explained above.