34. And come not near to the orphan's property except to improve it, until he attains the age of full strength. And fulfill (every) covenant. Verily, the covenant will be questioned about.

35. And give full measure when you measure, and weigh with a balance that is straight. That is good (advantageous) and better in the end.

The Command to handle the Orphan's Wealth properly and to be Honest in Weights and Measures

And come not near to the orphan's property except to improve it, until he attains the age of full strength.

meaning, do not dispose of the orphan's wealth except in a proper manner.

but consume it [the orphan's property] not wastefully and hastily fearing that they should grow up, and whoever (among guardians) is rich, he should take no wages, but if he is poor, let him have for himself what is just and reasonable (according to his labor). [4:6]

In Sahih Muslim it is recorded that the Messenger of Allah said to Abu Dharr:

"O Abu Dharr, I see that you are weak (in administering), and I like for you that which I like for myself. Do not let yourself be appointed as Amir over two people, and do not let yourself be appointed as guardian of an orphan's property."

And fulfill (every) covenant. meaning, everything that you promise people, and the covenants that you agree to, because the person who makes a covenant or a promise will be asked about it:

Verily, the covenant will be questioned about.

And give full measure when you measure. meaning, do not try to make it weigh less nor wrong people with their belongings.

and weigh with a balance meaning scales,

that is straight. meaning that which is not distorted nor that which will cause confusion.

that is good for you, in your daily life and in your Hereafter. So Allah says:

and better in the end. meaning, with regard to your ultimate end in the Hereafter.

That is good (advantageous) and better in the end.

Sa'id narrated that Qatadah said that this means "Better in reward and a better end." Ibn 'Abbas used to say: "O people, you are entrusted with two things for which the people who came before you were destroyed - these weights and measures."