Verses with the word becamest in the Old Testament (2 verses):

1 Chronicles 17:22
For thy people Israel didst thou make thine own people for ever; and thou, LORD, becamest their God.

Ezekiel 16:8
Now when I passed by thee, and looked upon thee, behold, thy time was the time of love; and I spread my skirt over thee, and covered thy nakedness: yea, I sware unto thee, and entered into a covenant with thee, saith the Lord GOD, and thou becamest mine.