Those who are merciful will be shown mercy by the Most Merciful. Be merciful to those on the earth and the One in the heavens will have mercy upon you.

Abdullah ibn Amr - Sunan Abu Dawud & Tirmidhi

He who does not show mercy will not be shown mercy.

Jarir ibn Abdullah - Sahih Bukhari & Muslim

Whoever fulfills the needs of his brother, Allah will fulfill his needs. Whoever removes a hardship of a Muslim, Allah will remove one of the hardships of the Day of Judgment from him.

Ibn Umar - Sahih Bukhari & Muslim