Samuel’s preparation for intercessory prayer, namely, the offering up an atoning sacrifice, is most significant (compare Luke 1:9-10). The term here used for a “lamb” does not occur in the Pentateuch; indeed it is only found besides this place in Isaiah 65:25. The offering is in accordance with Leviticus 22:27.
The Lord heard him - Better as in margin. The “answer” was not simply the granting the asked-for deliverance, but the great thunder 1 Samuel 7:10, which was “the voice of the Lord,” the same voice with which the Lord answered Moses Exodus 19:19; Psalms 99:6.