Sunan Abu Dawud
4666
Sahih Isnaad+2

Qais b. ‘Abbad said :I said to ‘All (Allah be pleased with him) : Tell me about this march of yours. Is this an order that the Messenger of Allah (May peace be upon him) had given you, or is this your opinion that you have? He said: The Messenger of Allah (May peace be upon him) did not give me any order; but this is an opinion that I have

Sahih IsnaadAl-Albani
Sahih IsnaadMuhammad Muhyi Al-Din Abdul Hamid