Berakhot 51A

במידי דלא ממאיס נמי, לסלקינהו לצד אחד וליברך? תרגמה רב יצחק קסקסאה קמיה דרבי יוסי בר אבין משמיה דרבי יוחנן: משום שנאמר ״ימלא פי תהלתך״.

The Talmud asks: With regard to a food item that does not become disgusting as well, let him shift it to the side and recite the blessing. Why need he spit it out? Rav Yitzḥak Kaskesa’a explained before R' Yosei bar Avin, in the name of R' Yoḥanan: One spits it out because it is stated: “My mouth will be filled with Your praise” (Psalms 71:8), meaning that one should recite God’s praises with his entire mouth, not merely half.

בעו מיניה מרב חסדא: מי שאכל ושתה ולא ברך, מהו שיחזור ויברך? אמר להו: מי שאכל שום וריחו נודף, יחזור ויאכל שום אחר כדי שיהא ריחו נודף?!

They raised a dilemma before Rav Ḥisda: One who ate and drank and did not recite a blessing, what is the ruling? Does he return and recite the blessing that he should have recited beforehand before he continues eating or not? In response, Rav Ḥisda said to them an analogy: Should one who ate garlic and the odor on his breath smells return and eat another garlic so that the odor on his breath will smell? That is to say, one must recite a blessing. Should one who committed a transgression and failed to recite a blessing before eating, remedy his situation by continuing to eat without reciting a blessing (Talmidei Rabbeinu Yona)?

אמר רבינא: הלכך אפילו גמר סעודתו, יחזור ויברך. דתניא: טבל ועלה, אומר בעלייתו ״ברוך אשר קדשנו במצותיו וצונו על הטבילה״.

Ravina said: Therefore, even if one finished his meal, he must return and recite a blessing. He cites a proof, as it was taught in a baraita with regard to the laws of immersion: One who was ritually impure who immersed himself in a mikveh and emerged, as he emerges he recites: Blessed…Who has made us holy through His mitzvot and has commanded us about ritual immersion. Evidently, in certain cases, one may recite the blessing after completing the act.