What are some Old Testament verses about service?

One of my favorite Old Testament books regarding service to others is Ruth. Boaz shows several wonderful examples of attention to the needs of Ruth and Naomi and makes effort to serve them.

Ruth 2:8-16

8Then Boaz said to Ruth, "Now, listen, my daughter, do not go to glean in another field or leave this one, but keep close to my young women. 9Let your eyes be on the field that they are reaping, and go after them. Have I not charged the young men not to touch you? And when you are thirsty, go to the vessels and drink what the young men have drawn." 10Then she fell on her face, bowing to the ground, and said to him, "Why have I found favor in your eyes, that you should take notice of me, since I am a foreigner?" 11But Boaz answered her, "All that you have done for your mother-in-law since the death of your husband has been fully told to me, and how you left your father and mother and your native land and came to a people that you did not know before. 12 The LORD repay you for what you have done, and a full reward be given you by the LORD, the God of Israel, under whose wings you have come to take refuge!" 13Then she said, "I have found favor in your eyes, my lord, for you have comforted me and spoken kindly to your servant, though I am not one of your servants."

14And at mealtime Boaz said to her, "Come here and eat some bread and dip your morsel in the wine." So she sat beside the reapers, and he passed to her roasted grain. And she ate until she was satisfied, and she had some left over. 15When she rose to glean, Boaz instructed his young men, saying, "Let her glean even among the sheaves, and do not reproach her. 16And also pull out some from the bundles for her and leave it for her to glean, and do not rebuke her."