This hadeeth was narrated in a mawqoof report from Abu'd-Darda' (may Allah be pleased with him) by Abu Dawood in his Sunan with a jayyid isnaad, as follows: Whoever says in the morning and in the evening Hasbi Allaah laa illaha illa huwa alayhi tawwakaltu wa huwa rabb al-arsh il-azeem (Sufficient for me is Allaah, there is no god besides Him; in Him have I put my trust and He is the Lord of the mighty Throne), seven times, Allah, may He be exalted, will suffice him for what concerns him, and it does not contain the additional phrase mentioned (of the affairs of this world and the Hereafter). This is a mawqoof hadeeth, the isnaad of which ends with Abu'd-Darda' and does not go back to the Prophet (blessings and peace of Allah be upon him), but it comes under the heading of a marfoo hadeeth, because such words could not be said on the basis of individual opinion. And Allah is the source of strength. End quote.
Reproduced from Islam QA