assalam ala kaum, there is a hadeeth in which Prophet Muhammad Sallahu wassalam said that a spacious house is part of muslim happiness however Prophet Muhammad and many Salaf us saliheen are Poor. so how to understand this hadeeth.Jazakhallah khair

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Perhaps you are referring to the Hadeeth narrated by Naafi’ ibn ‘Abdul-Haarith that the Prophet said: "A source of a happiness to the Muslim is to have a spacious dwelling, a righteous neighbor, and a comfortable mount." [Al-Bukhaari, Ahmad in his book Al-Musnad and Ibn Hibbaan in his Saheeh]

The wording of this Hadeeth reported by Ibn Hibbaan is as follows: "There are four reasons of happiness: a pious wife, a spacious dwelling, a righteous neighbor and a comfortable mount."

The wording of the Hadeeth reported by Ahmed reads: “A source of a happiness to the Muslim is to have a righteous neighbor, a comfortable mount and a spacious dwelling.”

What is meant by happiness according to the interpreters of Hadeeth is the happiness in this worldly life, i.e. comfort, and it does not mean the absolute happiness.

Al-Munaawi said in Faydh Al-Qadeer:

"This is the happiness of this worldly life, and not the happiness of religion. Happiness is of two kinds: absolute happiness and restricted happiness. The absolute happiness is the one in this worldly life and the Hereafter, and the restricted happiness is that which is restricted by something. The Prophet stated many things, and the one who is blessed with the three mentioned things will lead a happy life. He will be joyful and will be in perfect condition because of having these things, because these matters are things that benefit the body and they are a source of pleasure in this worldly life. However, a person may be happy in this worldly life and yet is not blessed with these things.” [End of quote]

This is true, because these matters are part of the reasons of happiness and not all of its reasons. A poor person may be happy without having a spacious house and a good mount. His happiness would be achieved by being a pious person, by being healthy in his body, preserved in his family and having righteous offspring who become the comfort of his eyes by their success and superiority.

On the contrary, a rich person may have a conformable mount, a spacious dwelling, while he experiences misery and weariness. This takes the form of being deprived from good health, for example, and not accepting the Decree of Allah and being discontent and displeased with it. He may be deprived of the blessing in his children and his money and so on.

We ask Allah to make us happy in this worldly life and in the Hereafter.

Allah knows best.