What is the relationship between sustenance (rizq) and one's job? Is the job itself considered sustenance?

A job is one of many means of sustenance, and it is in itself a facilitated provision from Allah. The multiple doors to provision are: piety towards Allah Almighty, abundant charity, supplication, and seeking forgiveness. This is based on the Almighty's saying: "And whoever fears Allah - He will make for him a way out And will provide for him from where he does not expect," and His saying: "And if only the people of the cities had believed and feared Allah, We would have opened upon them blessings from the heaven and the earth," and His saying: "And whatever thing you spend [in His cause] - He will compensate it; and He is the best of providers." Also, the Messenger of Allah, peace and blessings be upon him, said: "Whoever adheres to seeking forgiveness, Allah will make for him a way out of every worry, and a relief from every hardship, and will provide for him from where he does not expect." Sins and transgressions are among the causes of deprivation of sustenance, as the Prophet, peace and blessings be upon him, said: "Indeed, a servant is deprived of provision because of a sin he commits."