These are the most central and common melodic pathways in Maqam Rast. It is not sufficient to say that Rast uses Jins Secondary Rast in upward melodies, and Jins Nahawand in downward melodies, as traditional theory tends to over-simplify it (1/2-flat-7 on the way up, flat-7 on the way down). These ajnas certainly do pull in those directions, in terms of tonic emphasis and sayir (trajectory), but the melodic picture is more complex than that, and certainly both ajnas can be found moving in either diretion.
From Muwashshah "Sihtu Wajdan"
From "Hayrana Leh"
From "Aruh Li Meen"
And a later passage, also from "Aruh Li Meen"
This qanun taqsim really captures the poignancy - or pungency, if you will - of the nahawand modulation in Rast--from the opening of the Mawwal Rast "Fein Ya Gameel Wa3dak"
From the ending of the same Mawwal Rast "Fein Ya Gameel Wa3dak"
From "Ya Maal ish-Sham"
From the Mawwal Rast "Kull illy Habb Itnasaf"
You'll notice there are fewer examples of this than of the tremendously common descending/passing Nahawand. The first two use a raised 4th (leading tone to 5) to fully tonicize the Nahawand; and you'll also notice the use of Musta3ar - a passing tonicization of 3 that maintains the raised 4 - in conjunction with the Nahawand
From Muwashshah "Sihtu Wajdan"
From Mawwal Rast "Kull illy Habb Itnasaf"
From "Fakkaruni"