Al-Haq is the One Who IS Truth, Absolute Truth, Necessary and Real Existence. His (God's) existence is proven to be true and so is His Divinity. He makes the truth manifest by the power of His words, Who supports those whom He loves by His signs. Allah is the Truth, al-Haqq, who is worthy of being adored, Who is always there and Who never disappears, Whose presence is proven to have always been, since time immemorial, and forever - even before time and above time. His promise is the very truth; He has said in this regard: Surely the promise of Allah is true. (31:33)
His presence is a reality standing on its own merits, and there is no existence except through Him, and by Him, and He never moves and is above motion or anything physical or material. He permits the truth to manifest itself. He creates everything as His wisdom dictates. He is present in a way which permits no room for Him to be absent, nor different, nor extinct. Everything that exists is from Him, and to Him is its ultimate end.
Man's role in this attribute is recognizing that his existence can cease and therefore the only Truth is God. By living with this recognition, one should reflect this attribute with truth in his speech and actions.
Whenever the Prophet made tahajjud during the night, he would say:
"Lord! All Praise is due to You! You are the Lord of the heavens and the earth and everything in them! All Praise is due to You! You are the One Who sustains the heavens and the earth and everything in them! You are the Truth; Your speech is the truth; Your promise is the truth; meeting with You is the truth; Paradise is the truth; Hell is the truth; the Hour [of Judgment] is the truth!
Lord! To You have I submitted myself; in You have I believed; upon You have I relied; to You have I returned; for Your sake have I disputed with others, based upon Your truth have I arbitrated; so, I implore You to forgive my past faults and my future ones, what I have concealed and what I have manifested! You are my Lord! There is no god but You!"