Sofoniasza 3:13 Halacha: Kitzur Shulchan Arukh

A man has the moral obligation to keep his word even though he gave no deposit as yet, nor did he mark the article, nor was the transaction completed. [If the parties] agreed on the price neither [the buyer nor the seller] may back out. Whoever retracts whether buyer or seller is guilty of acting in bad faith, and the spirit of the Sages do not look kindly on him, for a Jew should keep his word, as it is written, "The remnant of Israel shall not commit injustice nor speak lies."¹⁰Zephaniah 3: 13. [In addition], a God fearing man should carry out even his unspoken decisions.¹¹Literally, the thoughts of his heart. If he decided to sell a certain article at a certain price and the buyer, not knowing [the seller's] innermost thoughts, offered him more, he should only accept from him the amount he had [originally] decided to charge, fulfilling the verse that states: "And speaks the truth within his heart."¹²Psalms 15: 2. The same rule applies to a buyer; if he decided to buy an article at a certain price, he may not change his mind. This rule applies to all matters in relationships between man and his neighbor. If he decided to do a certain favor [to someone] and is able to do it, he should fulfill his intention. But regarding his personal needs, if it does not involve the performance of a mitzvah, he need not fulfill even [intentions] expressed with his lips.

It is a positive mitzvah for the father to circumcise his son, or to grant the honor and appoint another Jew as his agent to circumcise him. The father should place the infant on the knees of the sandek, hand over the knife to the mohel, and stand by him during the circumcision, to indicate that the mohel is his agent. In the interval between the cutting of the foreskin and its laceration, the father recites the berachah, Asher kideshanu bemitzvosav vetzivanu lehachniso etc. "Who has sanctified us with His commandments and has commanded us to induct him into the covenant of our father Avrohom." You should make an effort to find the best and most righteous mohel and sandek. It is customary not to select as sandek, a man who had already been sandek at the circumcision of another one of his sons.¹See Ramah 265:11—Maharil. Also Tzava’as Rabbeinu Yehuda Hachassid. However, the Nodah Beyehuda Kama Responsa 86 says the custom is to permit it. See Chasam Sofer (Orach Chaim) Responsa 158 that you may give the honor more than once to the Rabbi of the city. If you have invited a mohel, it is forbidden to retract and invite another one, for it is said, "The remnant of Yisrael will do no injustice and will speak no falsehood."²Tzefanya 3:13. If you appointed a mohel, and in the meantime the mohel left the city, and the father, thinking that he would not return in time for the circumcision, appointed another (in his stead), but in the meantime the original mohel returned, he should perform the circumcision.