I found: You are my all in all by Dennis Jernigan
If you mean the numbers at the beginning, that is the key signiture.
Do you mean Mendelssohn? In Mendelssohn's Elijah there is an aria for tenor "If with all your hearts" which goes on, "ye truly seek me, ye shall surely ever find me. Thus, saith our God ...."
You can get it on www.iwannadownloadsheetmusicforflytoyourheart.com/selenagomezsheetmusic4u!
http://schmidtgracen.com/freefiles/heartandsoul.pdf