Rashi on I Samuel
Behold, obeying His command is better than a choice offering.23‘ה prefers the fulfillment of His command over the offering of voluntary sacrifices.
Rashi on I Samuel
To hearken [is better] than the fat of rams. This refers to, "Behold, obeying [is better] than a choice offering, and to hearken [is better] than the fat of rams."