Making vows to anyone other than Allah is an act of Shirk (associating others with Allah in His Divinity or worship).
Likewise, offering sacrifices to anyone other than Allah is also an act of Shirk. Allah (Glorified be He) says: (Part No. 1; Page No. 184)
And whatever you spend for spendings (e.g., in Sadaqah - charity for Allâh’s Cause) or whatever vow you make, be sure Allâh knows it all.
He also says:
Say (O Muhammad صلى الله عليه وسلم): "Verily, my Salât (prayer), my sacrifice, my living, and my dying are for Allâh, the Lord of the ‘Alamîn (mankind, jinn and all that exists).
He has no partner.
The Prophet (peace be upon him) said:
Allah curses the one who sacrifices to other than Allah…
Making vows is included in Allah's saying:
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.