SHIRK IS THE MOST DESTRUCTIVE OBSTACLE FOR THE SEEKER OF PERFECTION ...

Feb 4, '13 11:02 AM for everyone

God, the Glorious and the Exalted, has said:

And they were not commanded except to worship God, keeping religion pure for Him ... . (98:5)
Ikhlas in Persian means vizheh kardan' (to make exclusive'), that is, to purge a thing of everything else that has mingled with it. That which is meant here is that all of one's speech and action should be for the sake of seeking nearness to God, the Exalted, and exclusively for His sake, without being adulterated with any worldly or otherworldly purpose.
Indeed, to God belongs sincere religion. (39:3)

The opposite of sincerity is that there be some other purpose mingled with it, such as the love of honour and property, good name, or the hope of otherworldly reward, or salvation and deliverance from the chastisement of hell, all of which are signs of shirk. Shirk is of two kinds: open and concealed. Open shirk is idolatry, and all its other forms consist of concealed shirk. 

The Messenger of God, may God bless him and his Household, has said:

Amongst the people of my Ummah intentions contaminated with shirk are more invisible than the creeping of a black ant on a black rock in a dark night.

Shirk is the most destructive obstacle for the seeker of perfection in wayfaring.

So let him who hopes for the encounter with his Lord, work righteousness, and not include in his Lord's service anyone. (18:110)

And when the obstacle of concealed shirk is removed, wayfaring (suluk) and attainment (wusul) become easy:

If one is sincere to God for forty days, springs of wisdom, emanating from his heart, become manifest in his speech .

And safety from sin comes from God.