Praise be to Allaah.
Know that Allaah will never cause the reward of anyone who does a good deed to be lost, and al-qard al-hasan (a goodly loan lent for the sake of Allaah) is the best type of deed that will bring a person closer to Allaah.
But if your husband knows that a particular person will not fulfil a trust or will take a long time to repay a loan, there is no sin on him if he declines to lend him money or books.
But if a person is in difficulty and has no money, it is better to give him more time and treat him with kindness. Allaah says (interpretation of the meaning):
“And if the debtor is in a hard time (has no money), then grant him time till it is easy for him to repay…” [al-Baqarah 2:280].
If you ask for your husband’s rights, or if he asks for them himself, there is no sin on him for that, because it is his due, but he should be kind and considerate. The Prophet (peace and blessings of Allaah be upon him) said: “A man died and it was said to him: ‘What did you used to say (do, i.e., in your lifetime)?’ He said: ‘I used to engage in business with people, and I used to give the rich time to repay their debts and I used to deduct part of the debt for the poor’. So he was forgiven.”(Reported by al-Bukhaari, no 2216).
The person who borrows something has to give it back. Allaah says (interpretation of the meaning);
“Verily, Allaah commands that you should render back the trusts to those to whom they are due…” [al-Nisa’ 4:58]
It was reported from Abu Hurayrah (may Allaah be pleased with him) that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever takes people’s money with the intention of repaying it, Allaah will help him to repay it; whoever takes people’s money with the intention of wasting it, Allaah will destroy him.”(Al-Bukhaari, 2212).
Know that nothing is lost with Allaah, and that you will get back what you have lost in this world. You will receive hasanaat (good deeds) on the Day of Resurrection when people will be most in need of hasanaat. And Allaah is the source of strength.