One must focus and give one's full attention when reciting a blessing. It is forbidden to engage in any other activity when reciting a blessing.[1] This includes even minor gestures, movements, or other activities that don’t truly distract one from the recitation of the blessing. It is even forbidden to scan a Torah text while reciting a blessing.[2] One who engages in other activities while reciting a blessing is considered to be in violation of the verse "…and if you conduct yourselves casually with me."[3]

One area where people are in the habit of engaging in other activities while reciting a blessing is during Birkat Hamazon. Many people snap or point their fingers while reciting Birkat Hamazon in order to convey messages to others. This is completely inappropriate.[4] Some people even clean the area around them while in the midst of the Birkat Hamazon. One should be especially careful to focus when reciting Birkat Hamazon as it is a mitzva of the Torah.[5] Indeed, one should close one's eyes when reciting Birkat Hamazon or read it carefully from a text.[6] Some even recommend reciting every word out loud.[7]

There are a number of other instances where halachic authorities remind us not to engage in other tempting activities while reciting a blessing, as well.One such example is when reciting "asher yatzar" after using the bathroom. Asher yatzar should be recited with one's full attention and concentration, and one should not be engaged in any other activity when reciting it. Most authorities frown upon the widespread practice of drying one’s hands while reciting Asher Yatzar,[8] though there are those who justify this conduct.[9] So too, when travelling, it is preferable to recite tefillat haderech while standing still and not while driving.[10]

On Sukkot, one must be sure not to shake one’s lulav until the preliminary blessing(s) has been recited in its entirety.[11] Although not a blessing in the literal sense, it is especially crucial for one to be completely focused on the shema when reciting it, and not to be distracted in any way.[12] As such, one who is driving, and must say the shema in order not to miss the deadline, should pull over to the side of the road to recite it rather than do so while driving. One should never recite any blessing while walking.[13]

Nevertheless, in extenuating or pressing circumstances, there are grounds to permit engaging in some other activity while reciting a blessing. This is especially true if one would otherwise be unable to properly concentrate on the blessing unless one did so.[14] As such, one is permitted to engage in an activity that requires virtually no concentration while reciting a blessing, such as drying one’s hands, if necessary. So too, one may swat a fly while praying or reciting a blessing, if the fly is disturbing one's concentration.[15]

[1] OC 183:12, 191:3; Taz, OC 191:1; Shevet Hakehati 2:89.

[2] Mishna Berura 191:5.

[3] Vayikra 26:21.

[4] Aruch Hashulchan, OC 183:8.

[5] Ben Ish Chai, Chukat; Mishna Berura 64:10; Kaf Hachaim, OC 191:5.

[6] Mishna Berura 185:1; Kaf Hachaim, OC 191:5. Regarding one who had little or no concentration while reciting the Birkat Hamazon, see: Shulchan Aruch Harav, OC 185:1,2 and Aruch Hashulchan, OC 185:7.

[7] Mishna Berura 185:3.

[8] Od Yosef Chai, Vayetzei; Chesed L’alafim 5:2; Chemdat Avraham 3:2.

[9] Salmat Chaim 15,16; Be’er Moshe 8:42; Rivevot Ephraim 1:17; Orchot Rabbeinu Vol 1. p. 15, Vol. 3 p. 187.

[10] Berachot 30a; Tur, OC 110:10; OC 110:4.

[11] OC 651:37; Shaar Hatziun 651:37.

[12] OC 63:3.

[13] Kaf Hachaim, OC 46:54.

[14] OC 183:11.

[15] OC 191:3; Mishna Berura 191:5; Aruch Hashulchan. OC 183:8.