Albert Barnes Commentary 2 Samuel 7:18

"Then David the king went in, and sat before Jehovah; and he said, Who am I, O Lord Jehovah, and what is my house, that thou hast brought me thus far?" — 2 Samuel 7:18 (ASV)

Sat before the Lord - In the tent where the ark was. Standing or kneeling was the usual attitude of prayer (1 Kings 8:22, 54-55). Modern commentators mostly take the word here in the sense of waiting or abiding, not sitting; however, "sat" is the natural rendering. David sat down to meditate and then rose up to pray.