Reference for Pesachim 208:5
שיש מהן פותח (בהן) בברוך ואין חותם בברוך ויש מהן שחותם בברוך ואין פותח בברוך והטוב והמטיב פותח בברוך ואינו חותם בברוך
in some of these you commence with 'Blessed' but do not conclude with 'Blessed', while in others you conclude with 'Blessed' but do not commence with 'Blessed'; and [in the blessing] 'Who is good and doeth good [unto all]'<span class="x" onmousemove="('comment',' This is the third blessing (if the three which constitute Grace after Meals; v. Singer's Prayer Book pp. 280-285 for the whole, and p. 283 for the blessing immediately proceeding');"><sup>7</sup></span> you commence with 'Blessed' but do not conclude with 'Blessed'.<span class="x" onmousemove="('comment',' The blessings for precepts and fruits are generally short, and therefore 'Blessed' is not repeated at the conclusion. Blessings immediately 'preceding others: e.g., those of the Amidah (the 'Eighteen Benedictions') . As each ends with the formula, 'Blessed art Thou, O Lord, who' etc., the following does not commence with 'Blessed'. Similarly, the blessing immediately preceding the Shema' concludes with 'Blessed' etc., and the Shema' together with the blessing which follows it is regarded as one long blessing; hence that too does not commence with 'Blessed'. (That benediction itself ends with 'Blessed art Thou', etc.; hence the fourth one recited in the evening - v. n. 5 - which follows immediately after, likewise does not commence with 'blessed'.) The third blessing of Grace after meals, though immediately following a conclusion containing the formula, 'Blessed art Thou, O Lord', etc., commence with 'Blessed', notwithstanding the above general rule, because it was instituted in memory of the Jews slain at Bethar in 135 C.E. which marked the 'disastrous end of the Bar Cochba revolt; hence it was regarded as quite distinct and apart from the rest. It is indeed a lengthy benediction, but as much of it consists of synonyms for God it would be unfitting to repeat 'Blessed art Thou' in the conclusion.');"><sup>8</sup></span> [