What is the reward for a benevolent loan (Qard Hasan), and what is the reward for granting a debtor respite until he can afford repayment? And have there been any hadiths that encourage this?

The "Qard Hasan" (beautiful loan) is, in essence, spending in the way of Allah, seeking His pleasure. Some have interpreted it as sincerity of intention and generosity of spirit on the part of the one giving charity. Others have interpreted it as glorifying Allah (Tasbeeh), proclaiming His greatness (Tahleel), and spending on one's family. Allah multiplies the reward of the "Qard Hasan" manyfold. As for a loan (salaf) that yields no benefit for the lender, it carries half the reward of charity. Granting respite to someone in hardship or forgiving their debt is among the reasons for Allah's forgiveness and for one to be shaded on the Day of Judgment, and it carries the reward of charity every day.