Deuteronomy 23:21-23

KJV_Strongs(i)
  21 H5087 When thou shalt vow [H8799]   H5088 a vow H3068 unto the LORD H430 thy God H309 , thou shalt not slack [H8762]   H7999 to pay [H8763]   H3068 it: for the LORD H430 thy God H1875 will surely [H8800]   H1875 require [H8799]   H2399 it of thee; and it would be sin in thee.
  22 H2308 But if thou shalt forbear [H8799]   H5087 to vow [H8800]   H2399 , it shall be no sin in thee.
  23 H4161 That which is gone out H8193 of thy lips H8104 thou shalt keep [H8799]   H6213 and perform [H8804]   H5071 ; even a freewill offering H5087 , according as thou hast vowed [H8804]   H3068 unto the LORD H430 thy God H1696 , which thou hast promised [H8765]   H6310 with thy mouth.